Rami Abdul-Rahman of the Britain-based Syrian Observatory for Human Rights said the explosion took place on Wednesday in the village of al-Buraq, near the central city of Hama.
The area is government-controlled, which is why reports on the blast were slow to emerge, he said.
A mini-bus packed with explosives blew up near a bus stop where factory workers were waiting to go home after work, said Abdul-Rahman. The dead included 11 women. He said the factory makes military supplies, but not weapons.
"These people work for the Ministry of Defense, but they are all civilians," he said "There was no one from the military" killed in the blast.
Syria's state news agency reported the explosion on Wednesday evening, saying "terrorists" detonated a car bomb near a factory. It did not say what the factory produced or specify the number of dead and wounded. The regime refers to rebels fighting to topple President Bashar Assad's government as terrorists.
No one has claimed responsibility for the blast, which resembled others in recent months that appeared to target buildings associated with Syria's military and security services.
Some of the bombings have been claimed by an al-Qaida-linked group fighting alongside the rebels, Jabhat al-Nusra, which the U.S. had designated as a terrorist organization.
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In violence Friday, the Observatory reported clashes and regime shelling in the southern and eastern sectors of the Syrian capital, Damascus, including in the restive suburb of Moadamiyeh, where six people were killed by government shelling overnight.
Syria's crisis began with peaceful protests in March 2011 and evolved into a civil war as the opposition took up arms to fight a government crackdown on dissent. The U.N. said last month that more than 60,000 people have been killed in the conflict.
Press; By BEN HUBBARD]
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