Syrian government warplanes killed at least 60 civilians including a dozen children in two days of airstrikes on Islamic State-held territory at the weekend, activists said on Monday.
President Bashar al-Assad's military has stepped up an aerial campaign over the last three months against Islamic State, an al-Qaida offshoot that controls about a third of Syria's territory, much of it desert in the north and east.
The airstrikes have hit a number of Islamic State targets but have also killed many civilians in territory under the group's control.
The death toll included 41 killed during airstrikes on Saturday that hit a bakery run by Islamic State in their stronghold of Raqqa city in the north, the Britain-based Syrian Observatory for Human Rights said.
Another 19 civilians were killed in the eastern Deir al-Zor province, which borders Iraq and, like Raqqa province, is almost entirely controlled by Islamic State militants.
The Observatory, which monitors violence in Syria through a network of sources on both sides, did not say how many militants were killed in the strikes, but in an earlier report it said at least 15 had been killed in the Raqqa strikes.
One Raqqa-based activist told Reuters the dead from the bombardment included eight members of one family, that of Khaled al-Haj Omar, and four from another family whose remains have not been found.
The youngest was seven-year-old Ibrahim al-Abed, he said. Among the women killed were Ayesha Hassan, 60, and 18-year-old Zeina al-Ahmad, the activist said.
Confrontations between Islamic State militants and Assad's forces have escalated sharply since the Islamists made lightning advances against Iraqi government forces in June and declared it was establishing a caliphate in territory it controls on both sides of the border.
Since then Islamic State has killed hundreds of Syrian government forces and seized three military bases in Raqqa province.
Syria's air force has bombed the group's positions, even as U.S. warplanes strike the group on the other side of the border in Iraq.
More than 190,000 people have been killed in Syria's conflict since it started more than three years ago, according to the United Nations. The daily death toll from shelling, gunbattles, airstrikes and executions regularly rises to more than 200 per day.