Car bomb kills 20 in Syria after Red Cross workers kidnapped

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(CNN) -- The bombs can explode anywhere, at any time. But after two years of civil war, Syria's unpredictable violence can still horrify.

At least 20 people were killed, including a child, when a car bomb exploded Monday in northwestern Syria, opposition activists said.

The blast rocked the Idlib province town of Darkush, on the border with Turkey, the London-based Syrian Observatory for Human Rights said.

The death toll is expected to rise because dozens are wounded, including some in critical condition, the opposition group said.

Red Cross: Seven aid workers kidnapped; four released

Even humanitarian workers aren't safe in the country.

On Sunday, gunmen kidnapped seven aid workers in northwestern Syria, officials said. Four of them -- three from the Red Cross and one from the Syrian Red Crescent -- were released "safe and sound" Monday, said Ewan Watson, a spokesman for the International Committee of the Red Cross.

Watson said he'd have no details about the freed workers' identities or current location until the other three workers are freed.

All seven were snatched in Idlib province, where they were trying to deliver medical supplies.

The state-run Syrian Arab News Agency said a terrorist group opened fire on the workers' vehicle and then abducted them.

ICRC spokesman Simon Schorno said his agency has been in contact with various armed groups to try to find the kidnapped workers, but it's still unclear who might have them.

"It's very difficult to say precisely at this point," Schorno said Monday. "There are lots of rumors flying around, and we don't really want to speculate."

But the kidnappings won't deter the Red Cross from continuing its work in the war-torn country.

"There is no intention for the Red Cross to stop its action in Syria," Schorno said. "In fact, the needs are just humongous in this country."

More than 2 million refugees have fled the country, but millions more are internally displaced as the incessant warfare zeros in on residential neighborhoods.

The United Nations' refugee agency says it is "stretched to the limit" by the constant flow of refugees spilling across borders.

Syria's descent into civil war began in March 2011, when President Bashar al-Assad's regime forcefully cracked down on peaceful anti-government protesters.

That conflict spiraled into an armed uprising and a 2-year-old crisis that the United Nations says has claimed more than 100,000 lives.

Destroying chemical weapons

While the vast majority of deaths in Syria have been from so-called conventional warfare, the confirmed use of chemical weapons in recent months has elevated the war's profile around the world.

On Monday, Syria became formally bound by the international treaty banning chemical arms, according to the Organisation for the Prohibition of Chemical Weapons.

The head of the agency, which trying to rid Syria of its chemical stockpile, said both the government and rebels have been cooperative. But much remains to be destroyed, Ahmet Uzumch, chief of the Organisation for the Prohibition of Chemical Weapons, told CNN's Frederik Pleitgen.

"Their stockpiles are quite substantial," Uzumch said. "We have about over 20 sites to be visited by the end of this month at least once."

Production facilities have to be deemed ineffective by the end of the month, too.

The rest of the weapons have to be inventoried. Once the inventory is complete, they will be destroyed, Uzumch said.

But the weapons won't be destroyed where they are stored; they'll have to be moved to a safer place, in some cases to other countries.

On the global scale, Uzumch said the OPCW is pretty close to eradicating chemical weapons worldwide. He said it will take four to five years to destroy the stockpiles they know about.

But six countries have yet to join sign on to the Chemical Weapons Convention, so it's not clear what their possible stockpiles might look like.