Syrian activists said Wednesday that dozens of people were killed or missing after an airstrike the day before leveled a school near the Islamic State-held city of Raqqa where displaced families had sought refuge.
The activist-run group Raqqa is Being Slaughtered Silently said some 50 families had been sheltering at the school in the northern Syrian village of Mansoura and that their fate was still unknown. Mansoura is 26 kilometers (16 miles) west of Raqqa, the de facto capital of the extremists' self-described caliphate, and is under their control.
The Britain-based Syrian Observatory for Human Rights said 33 bodies had been pulled from the rubble. The two organizations rely on local contacts to smuggle news out of Islamic State-held territory.
It was not immediately clear who carried out the airstrike. Syrian Kurdish forces have been advancing on Raqqa under the cover of U.S.-led coalition airstrikes and are now 8 kilometers (5 miles) north of the city. Syrian and Russian aircraft have also carried out strikes against the ISIS group.
Elsewhere in Syria, insurgents advanced on government-held towns and positions north of the central city of Hama. An al-Qaida-linked group spearheaded the assault, launched Tuesday, by detonating a car bomb in the nearby town of Souran.
The activist-run Hama Media Center said the rebels had reached the village of Khatab, 10 kilometers (6 miles) northwest of government-held Hama. State media reported fighting on the outskirts of the village and Souran.
The offensive coincides with a concentrated effort by opposition forces to breach government lines in the eastern neighborhoods of the capital, Damascus. That operation is also spearheaded by the al-Qaida-linked Levant Liberation Committee.
In Damascus, the insurgents were pinned down in industrial zones in the city's east. Government airstrikes and artillery fire echoed through the capital, and smoke could be seen rising above the opposition-held Jobar neighborhood. Residents close to the front lines on the government side were seen leaving their buildings with whatever belongings they could pack in their suitcases.
The uptick in fighting precedes the resumption of U.N.-mediated talks between the government and the opposition in Geneva, slated for Thursday.
U.N. Special Envoy to Syria Staffan De Mistura called the developments "alarming," but said the invited delegations would be in attendance "with, I hope, serious intentions to follow up the political process."
He spoke to reporters in Moscow, following a meeting with Russian Foreign Minister Sergei Lavrov.
Lavrov accused militants of carrying out more "terrorist attacks," which he said were "aimed at disrupting or complicating the Geneva talks."
Russia is a steadfast ally of Syrian President Bashar Assad.
Associated Press writer Albert Aji in Damascus, Syria and James Heintz in Moscow contributed to this report.