Syrian government forces have killed dozens of civilians in air raids in the northern city of Aleppo, activists say.
The Syrian Observatory for Human Rights (SOHR) says about 90 people - most of them civilians - died when helicopters dropped barrel bombs on Saturday.
Aleppo has been the focus of bitter fighting between President Bashar al-Assad's forces and rebels.
Meanwhile militants linked to al-Qaeda are reported to have killed the leader of a rival Islamist militia there.
Fighters from the Islamic State of the Iraq and the Levant (ISIS) killed Adnan Bakkour during a raid on the base of rivals, the Tawheed Brigades, according to SOHR, a UK-based group that monitors the conflict.
Attacks using barrel bombs and Scud missiles by President Assad's forces are believed to have killed hundreds of people in Aleppo since the conflict began almost three years ago.
The use of the barrel bombs - essentially barrels packed with explosives - has been condemned by rights groups as indiscriminate.
Among those killed on Saturday were 33 civilians, including women and children, who died in a bombardment of the al-Bab area of Aleppo, while at least 13 civilians were killed in eastern areas of the city, SOHR said.
Ten rebel fighters from the jihadist group al Nusra Front were also killed by barrel bombs in the al-Shaar area, the monitoring group said.
The air raids reportedly continued on Sunday but the number of casualties is not known.
Russia has blocked statements at the UN Security Council condemning the Syrian government's use of air strikes against civilians in Aleppo.
Syrian government forces have launched an offensive in recent weeks on rebel-held areas in the east of the city, with Defence Minister Gen Fahd al-Freij visiting the province on Friday.
Quoted by state news agency Sana, he praised the army for its "great victories and their liberation of many areas in Aleppo".
More than 100,000 people have been killed and millions forced to flee their homes in Syria's nearly three-year civil war.