Syrian government forces have launched airstrikes in Raqqa province, killing at least 50 people, as part of its offensive against the Islamic State group who control the area.

The Syrian Local Coordination Committees said on Saturday that at least 15 Islamic State fighters and 35 civilians, including a woman and three children, were killed when missiles hit the Tal Abyad neighbourhood as well as a crowded bakery.

"Regime warplanes carried out eight air strikes targeting Raqqa and its surroundings," said Syrian Observatory for Human Rights (SOHR) director Rami Abdel Rahman, who also claimed the bakery was run by the IS group.

The airstrikes smashed parts of buildings, set cars alight and crushed people under rubble, according to a video of the aftermath uploaded on social media networks. Al Jazeera could not indepedently confirm the veracity of the video.

The strikes come amid a stepped-up military campaign by President Bashar al-Assad's regime targeting IS positions in northern and eastern Syria, among the targets on Saturday were a building housing an IS Islamic court and a training camp.

Three-year-old uprising

IS fighters took control of the Tabqa miliary air base in Raqqa province last month after fierce battles, and later executed scores of captured Syrian soldiers. The air base is one of the most significant governement military facilities in the area.

The Syrian government has suffered heavy losses against the armed group, with hundreds of soldiers and pro-government fighters killed in recent months as it overran oil fields and military bases.

In a separate development, the Syrian Observatory said the number of people killed in a Friday airstrike targeting a Syrian rebel-held area in the northern Aleppo city has risen to 15.

The Syrian military offensive comes as the United States announced the formation of a coalition to fight the Islamic State. US President Barack Obama said on Friday that key NATO allies stood ready to join the US in military action to defeat the armed group that controls vast swathes of land in Iraq and Syria.

The Syrian government has said it should be a partner in the fight against Islamic State. But Western states, which have backed the more than three-year-old uprising against Assad, have dismissed the idea of co-operating with Damascus. The West see Assad as part of the problem.

Source: Al Jazeera and agencies