Between 150-250 workers at a cement factory near Syrian capital Damascus have disappeared after an attack this week by the Islamic State terrorist militia, a monitoring group said Thursday.
"Our information says that between 150-250 workers went missing and they might have been kidnapped by Islamic State and taken to an unknown destination," head of the Syrian Observatory for Human Rights, Rami Abdel-Rahman, told dpa.
"We do not know their whereabouts yet," he said.
The Britain-based watchdog said earlier that contact has been lost with dozens of the workers since the extremists attacked the plant in the town of al-Dumeir, north-east of Damascus, on Tuesday.
At least 20 Syrian soldiers and allied paramilitaries have been killed in clashes with Islamic State jihadists in al-Dumeir in the last 48 hours, the Observatory said.
There was no official comment in Damascus.
Meanwhile, Syrian state television said government forces had shelled unspecified posts in al-Dumeir, inflicting casualties among whom the broadcaster called "terrorists."
It made no mention of the reported disappearance of the workers.
Islamic State's latest attacks near Damascus are seen as retaliation for the military setbacks suffered by the al-Qaeda splinter group elsewhere in Syria.
Last month, Syrian regime forces, backed by Russian warplanes, drove Islamic State from the ancient city of Palmyra that the militants had controlled for 10 months.
On Sunday, Syrian forces recaptured the town of al-Qaraytain, about 100 kilometres south-west of Palmyra, from Islamic State.
Islamic State and al-Qaeda's Syria branch, al-Nusra Front, are excluded from a major ceasefire that has been in force in Syria since February.
The US-Russian-brokered truce is aimed at boosting indirect peace talks between the Syrian government and the opposition.
A new round of UN-sponsored Syria talks is expected to start in Geneva next week.
The ceasefire is also aimed at letting relief aid into Syrian towns besieged by regime forces and rebels.
In Geneva, UN envoy Jan Egeland the Syrian government has blocked deliveries of international aid to beleaguered areas in the past days, warning that the slowdown of humanitarian efforts can hurt the peace process.
Government authorities denied passage to four convoys that would bring aid to some 300,000 people in cities besieged by the army, he said, adding that opposition fighters blocked one Red Crescent aid delivery.
"I'm disappointed, I am disheartened of what we achieved over the last week," said Egeland, who chairs a task force of global and regional powers that are supposed to negotiate humanitarian access with the conflict parties.
"It is very dangerous to lose the momentum with humanitarian work" because this can affect the peace talks and Syria's fragile truce, he added.