U.S-led coalition planes bombed an Islamic State-controlled town near the Euphrates Dam in northern Syria a day after the launch of a new phase of a campaign to capture the militants' stronghold of Raqqa, activists and the militants said on Sunday.

Activists confirmed reports released by the militants' news agency Amaq, which said four raids in the last 24 hours hit the town of Tabqa west of Raqqa, located near Syria's largest dam, at the southern end of Lake Assad on the Euphrates.

A video released by Amaq showed extensive damage to a commercial center in the town but did not mention any casualties.