Opposition activists say warplanes have carried out several airstrikes in Syria's Hama, killing at least 25 people, amid a lightning advance by insurgents on government-controlled areas of the central province.

The Britain-based Syrian Observatory for Human Rights says Thursday a series of airstrikes in northern Hama province has killed at least 25 civilians, including six children.

The Hama-based Syrian Press Center, another activist group, says at least ten people were killed when warplanes struck a crowd of people displaced from Suran, a town north of Hama city that was seized by opposition fighters. It says another 15 people were killed further to the west.

Syria's state news agency, SANA, says warplanes killed 10 "terrorists" in northern Hama.

Insurgents have been pushing toward Hama city, seizing government positions in the north.