Forces seize second district

US-backed Syrian fighters yesterday seized a second district of Raqa and launched a renewed assault on a base north of the city, as they pursued an offensive against the Islamic State group.

The Syrian Democratic Forces (SDF) broke into Raqa earlier this week after announcing the start of a final assault on the IS-held city.

Yesterday, the Arab-Kurdish alliance said its fighters had "liberated the neighbourhood of Al-Romaniya on the western front of Raqa, after two days of continued clashes".

It was the first time the SDF was reported to have taken a western district of Raqa, after seizing control of the Al-Meshleb district in the east.

The western approach to the city was littered with mangled motorcycles and unexploded mortar rounds fired by IS, AFP's correspondent there said.

Inside the city, SDF commanders took up positions on the rooftops of modest one-storey homes that were eerily empty of civilians.

Artillery, sniper fire and air strikes rang out throughout yesterday, and pillars of thick black smoke snaked up from the city skyline.

Bombardment had taken chunks out of the white dome of a neighbourhood mosque, and the notorious black IS flag hung limply from a roof.

After its capture by IS in 2014, Raqa city emerged as a key hub for IS's operations in Syria, neighbouring Iraq, and beyond.

The SDF -- an Arab-Kurdish alliance formed in 2015 -- spent seven months tightening the noose on Raqa city from the north, east, and west.

While it has advanced steadily against IS inside east and west Raqa, it has made less progress on the northern front, where jihadists are using a military base and adjacent sugar factory to defend the approach into the city.

An estimated 300,000 civilians were believed to have been living under IS rule in Raqa, including 80,000 displaced from other parts of Syria.

Thousands have fled in recent months, and the UN humanitarian office estimates about 160,000 people remain in the city.

They have no electricity and were facing severe water shortages, according to the activist collective known as Raqa is Being Slaughtered Silently.

The Observatory said that coalition air strikes on Saturday killed 24 civilians inside Raqa, up from an earlier toll of 13.