An air strike on a high school killed 16 people, most of them students and teachers, in a rebel-held city in northern Syria on Sunday, a monitoring group said.
"The Syrian air force bombed a technical high school in the city of Raqa, killing 16 people, among them 10 students aged under 18, and wounding many others, some critically," said the Syrian Observatory for Human Rights, updating an earlier toll.
The Britain-based group posted video footage showing mangled bodies, one lying under schoolbooks. Its authenticity could not immediately be verified.
"There was panic, with children crying as they sought to take shelter," the Observatory quoted a survivor as saying.
Raqa, on the Euphrates River valley 160 kilometres (100 miles) east of the main northern city of Aleppo, is the only provincial capital entirely in rebel hands.
Captured from government forces on March 6, the city is now largely controlled by Al-Qaeda loyalists of the Islamic State of Iraq and the Levant.
The air strike came after rebels launched an overnight attack on army positions in Nasseriya al-Qalamun, north of Damascus, killing at least 19 soldiers and wounding 60, the Observatory said.
"There were also losses in the ranks of the rebels, who succeeded in capturing several positions," it added, without giving a figure.
Meanwhile, the bodies of 14 pro-regime militiamen killed in Zamalka east of Damascus were transported to their native city of Homs, said the Observatory.
The army said it killed "a large number" of rebels in Nashabiyeh, north of the capital.
Violence has raged for months around Damascus, as the army has fought hard to keep the rebels out of the city.
Activists say the army has for months besieged rebel-held areas, mainly east and southwest of Damascus.
The Observatory, meanwhile, updated its toll to 34 for a Friday car bombing at a mosque in Rankus north of the capital.
Among the casualties were four children, it said.
In southern Syria, after four days of fighting that killed 26 soldiers and "a large number" of rebels, among them seven non-Syrians, the opposition took a customs building and an area linking Daraa to the Golan Heights, the Observatory said.
A security source downplayed the development, saying: "We cannot say the terrorist groups have taken over this or that position, because the situation shifts. The fighting continues."
Amman, meanwhile, protested to Damascus after a shell struck the northern Jordanian city of Ramtha three days ago.