Offensive to liberate Raqa begins

US-backed fighters broke into the city of Raqa yesterday as they launched a final assault to drive the Islamic State group from its de facto Syrian capital.

The attack on the northern city at the heart of IS's Syrian territory has been seven months in the making and is backed by air support, military advisers and weapons deliveries from the US-led coalition.

Seized by the jihadists in early 2014, Raqa became notorious as a hub for IS's operations in Syria, Iraq and beyond.

The city has been the scene of some of IS's worst atrocities, including gruesome executions, public displays of bodies and the trafficking of women.

It was one of the twin pivots of IS's so-called "caliphate," with Mosul in neighbouring Iraq -- where US-backed forces are also bearing down on the jihadists.

After months sealing off access routes to the city from the east, north and west, the US-backed Syrian Democratic Forces yesterday entered city limits for the first time.

"Our forces entered the city of Raqa from the eastern district of Al-Meshleb," SDF commander Rojda Felat told AFP, adding that clashes were also raging on the city's northern outskirts.

"They are fighting street battles inside Raqa now, and we have experience in urban warfare," she said.

The advance was backed by heavy air strikes by the US-led coalition, the Syrian Observatory for Human Rights said.

The coalition began its air campaign against IS in Iraq in August 2014, expanding its operations to Syria the following month.

The coalition appears keen to expel IS from its last major urban bastions before the "caliphate" turns three years old later this month.