(CNN) -- The United States is doing what it must to "take the fight to terrorists," leading a coalition of Arab nations in a series of airstrikes against the so-called Islamic State terror group in Syria, U.S. President Barack Obama said Tuesday.
At the same time, the United States took action -- on its own -- against another terrorist organization, the Khorasan Group. Obama described its members as "seasoned al Qaeda operatives in Syria."
U.S. officials said the group was plotting attacks against the United States and other Western targets.
The plots against the United States were discovered by the intelligence community in the past week, an intelligence source with knowledge of the matter told CNN. The source did not say what the target may have been, but said the plot potentially involved a bomb made of a nonmetallic device like a toothpaste container or clothes dipped in explosive material.
A plot involving concealed bombs on airplanes "was just one option they were looking at," a U.S. official said.
"Once again, it must be clear to anyone who would plot against America and try to do Americans harm that we will not tolerate safe havens for terrorists who threaten our people," Obama said in televised remarks from the White House.
But Syria warned the United States not to repeat the "fiasco in Iraq by undertaking the same kind of blind military attacks," Bashar Ja'afari, Syria's ambassador to the United Nations, told CNN.
The airstrikes in Syria began early Tuesday morning local time. Bahrain, Saudi Arabia, the United Arab Emirates and Jordan took part in airstrikes on ISIS targets, the U.S. military said. Qatar played a supporting role, the U.S. military said.
Noting that he had "made clear that America would act as part of a broad coalition," the President said: "That's exactly what we've done."
"The strength of this coalition makes it clear to the world that this is not America's fight alone," Obama said at the White House. "Above all, the people and governments in the Middle East are rejecting ISIL and standing up for the peace and security that the people of the region and the world deserve." ISIL is another acronym referring to the terrorist group, which calls itself the Islamic State.
While the President touted the coalition, the U.S. Department of Homeland Security issued a bulletin warning law enforcement agencies to be on heightened alert for lone-wolf terror attacks on U.S. soil in wake of the airstrikes, a U.S. law enforcement official told CNN.
There is bipartisan support in Congress for the U.S. military actions, Obama said, adding that "America is always stronger when we stand united. And that unity sends a powerful message to the world that we will do what's necessary to defend our country."
Strikes came in three waves
The strikes were "very successful," Pentagon spokesman Rear Adm. John Kirby said Tuesday.
While the military can't comment in detail about future plans, the strikes "were only the beginning," Kirby added.
The strikes came in three waves, with coalition partners participating in the latter two, Army Lt. Gen. William Mayville Jr. said Tuesday. The first wave, which mostly targeted the Khorasan Group, started at 5:30 a.m. (8:30 p.m. ET Monday) and involved U.S. ships firing missiles into eastern and northern Syria.
The second wave, 30 minutes later, involved planes striking northern Syria, with targets including ISIS headquarters, training camps and combat vehicles. The third wave, begun shortly after 7 a.m., involved planes targeting ISIS training camps and combat vehicles in eastern Syria, Mayville said.
It's too early to say what effect the U.S. strikes had against the Khorasan Group, Mayville said.
Monitor group estimates at least 70 ISIS militants killed
The airstrikes against ISIS focused on the city of Raqqa, the declared capital of ISIS' self-proclaimed Islamic State. But other areas were hit as well.
The operation began with a flurry of Tomahawk missiles launched from the sea, followed by attacks from bomber and fighter aircraft, a senior U.S. military official told CNN.
The goal: Taking out ISIS' ability to command, train and resupply its militants.
In all, 200 pieces of ordnance were dropped by coalition members, and four dozen aircraft were used, a U.S. official told CNN. About 150 weapons used were precision-guided munitions. The United States fired 47 Tomahawk missiles, eight of them against Khorasan targets.
The number of casualties was not immediately clear. But U.S. Central Command said the strikes damaged or destroyed ISIS targets including fighters, training compounds, command-and-control facilities, a finance center and supply trucks.
The Syrian Observatory for Human Rights said at least 70 ISIS militants were killed and more than 300 were wounded. But CNN and other news outlets were unable to confirm the figures.
CNN national security analyst Fran Townsend said these attacks focused on infrastructure, but were just the beginning.
Eventually, she said, there will likely be "a real campaign to go after leadership targets."
Celebration amid fear
For months, civilians in Raqqa have been living under the harsh rule of ISIS after militants took over their city, which had been one of Syria's most liberal cities. The group now controls much of their lives, imposing a strict brand of Sharia law and doling out barbaric punishments, such as beheadings and crucifixions.
Abo Ismail, an opposition activist inside Raqqa, said Tuesday that residents were elated to see the U.S. attacking ISIS targets there.
But at the same time, he said, ISIS has increased security in the city.
"I would dance in the streets, but I am too afraid," Ismail said.
A U.S. intelligence official said that while law enforcement is aware the airstrikes against ISIS in Syria could incite a response, there is no evidence to suggest any terrorist strike is in the works against the United States.
A U.S. 'diplomatic achievement'
The involvement of several Mideast nations is "a remarkable diplomatic achievement," said CNN political commentator Peter Beinart. "I don't think it was expected that there would be this much Arab support."
Former CIA counterterrorism official Philip Mudd said the inclusion of Sunni-majority countries fighting a radical Sunni militant group sends a strong message.
"Prominent religious leaders have said ISIS is not representative of Islam, and now you have countries that are coming to the fore to attack it," he said.
Bahrain's state-run media said the country's air force "carried out earlier this morning along with the air forces of the Gulf Cooperation Council (GCC), allied and friendly countries, air strikes against a number of selected targets of terrorist groups and organisations, and destroyed them, an authorised source at the Bahrain Defence Force (BDF)'s General Headquarters said."
The UAE air force "launched its first strikes against ISIL targets last evening," the Foreign Ministry said.
Jordan's official news agency, Petra, said the country carried out airstrikes against terrorist groups in Syria. It cited an unnamed military official as explaining the strikes were needed due to increased incidents and infiltrations along the border in the past two months. The report said Jordan will carry out further strikes if border attacks keep up.
British Defense Secretary Michael Fallon said, "The UK supports the airstrikes launched by the U.S. and regional allies last night," the Defense Ministry said on Twitter. The government "continues to discuss what further contribution the UK may make to international efforts to tackle the threat from ISIL," the ministry added.
The Syrian regime was notified of the U.S. plan to take direct action against ISIS inside Syria, a senior State Department official told CNN on Tuesday.
The United States did not seek the regime's permission, nor did it coordinate with the Syrian government, the source said, adding that Secretary of State John Kerry did not send a letter to the regime.
On state-run media, Syria said its U.N. representative was informed Monday that the U.S. and some of its allies would target ISIS. Syria also said its foreign minister, Walid al-Moallem, "received a letter from his American counterpart delivered by the Iraqi foreign minister which informed him that 'the U.S. will target the positions of the ISIS terrorist organization, some of which are in Syria.'"
A 'punch in the nose'
Until now, ISIS has been able to take over cities and operate in Syria with near impunity. Now, it's coming under attack.
"This is the punch in the nose to the bully that we talked about on the playground," former Delta Force officer James Reese said. "ISIS is the bully, and we just punched him in the nose."
The United States has been conducting airstrikes against ISIS in Iraq, but never before against the militant group in Syria.
Syrian opposition: Finally
With the airstrikes, the United States enters a new level of engagement in the ongoing Syrian civil war.
For three years, Syrian rebels have been clamoring for Western military help as they battle regime forces and seek an end to four decades of al-Assad family rule. But the United States has resisted military action in Syria.
The difference now? ISIS, its bloody takeover of stretches of Iraq and Syria, and its threat to Americans.
"I have made it clear that we will hunt down terrorists who threaten our country, wherever they are," President Barack Obama said in a September 10 speech.
"That means I will not hesitate to take action against ISIL in Syria, as well as Iraq. This is a core principle of my presidency: If you threaten America, you will find no safe haven."
The Free Syria Foreign Mission said it was elated by the U.S. strikes.
"Thank God. What a momentous day -- a day that we have been looking forward to for so, so long," the Syrian opposition group said. "It's a big step forward, but we are nonetheless cleareyed that it will be a prolonged campaign to defeat ISIS."
Ironically, the U.S.-led offensive might please the Syrian dictator, Bashar al-Assad, as much as it does the Syrian opposition.
"It helps him because we're taking out one of the threats to his regime," said retired Air Force intelligence officer Lt. Col. Rick Francona.
"If we destroy ISIS, which we're committed to do ... that takes the biggest player off the table. And all he has to worry about is the smaller, less effective al Qaeda in Syria -- al-Nusra -- and the (rebel) Free Syrian Army, both of whom he has bested in the past couple of years."
British hostage shown in new video
John Cantlie, a British journalist held captive by ISIS, spoke in a second video posted by the terrorist group overnight.
He said Western governments are moving toward war, adding, "It's all quite a circus."
Since Cantlie is delivering ISIS propaganda and speaking under duress, CNN is not showing the video on its platforms.
Too little, too late?
But some say the United States waited too long to act against ISIS in Syria.
"The airstrikes have come much too late in the case of Syria, where the IS militants have had over a year to entrench themselves within the region -- especially the province of Raqqa," said Natasha Underhill, an expert on Middle East terrorism at Nottingham Trent University.
She said ISIS "is deeply entrenched in both Syria and Iraq, and it may take a lot more than airstrikes to make a dent in their campaign of creating an even larger caliphate across the Middle East."
Not over yet
Mudd said Tuesday's attacks were "just the start."
"This is not a definitive blow," the former CIA official said.
"When this gets interesting to me ... is six months down the road, when a second-tier ISIS commander starts to create some sort of cell to recruit foreigners from Europe or the United States or Canada into Syria. Do we still have the will and capability, and the intelligence, to locate that person, or that group of people, and put lead on the target?"