BEIRUT (REUTERS) - More than 7,000 people have escaped ISIS control in the Tabqa area west of the Syrian city of Raqqa since last week, US-backed local forces fighting the militants said on Friday (March 31).

The Syrian Democratic Forces, an alliance of Kurdish and Arab milita fighters, has been battling the Islamic State in Iraq and Syria around Tabqa, nearly 40km west of Raqqa city.

Last week, they captured the northern entrance to the Tabqa Dam, a major target in their military campaign to isolate and capture Islamic State's biggest urban stronghold.

With air strikes and special ground forces from the US-led coalition, the SDF has been advancing on Raqqa city from the north, east and west.

Thousands of families have arrived at SDF-held positions since last week after managing to flee Tabqa and nearby villages, the SDF said.

The Syrian Observatory for Human Rights, a British-based organisation that monitors the war, said clashes and air strikes had pushed nearly 3,000 people to escape those areas over the past week.

The offensive to capture Raqqa will last a number of months, the operation's commander told Reuters earlier on Friday.