A US-backed alliance of Kurdish and Arab forces pushed Thursday into the ISIL Takfiri group’s bastion city of Manbij in northern Syria, a monitoring group said.

A US-backed alliance of Kurdish and Arab forces pushed Thursday into the ISIL Takfiri group's bastion city of Manbij in northern Syria, a monitoring group said.

The Syrian Democratic Forces managed to enter the city with support from air strikes by a US-led coalition, the Syrian Observatory for Human Rights said.

"The SDF entered Manbij from the south under cover of coalition air raids," said Observatory chief Rami Abdel Rahman, whose Britain-based group.

He said there was "fierce street fighting between buildings" and that at least two SDF fighters had died when a bomb went off in a residential building.

Abdel Rahman said the SDF was able to break through ISIL defenses a few hours after taking control of a village on the city's southwestern outskirts.

He said progress was likely to be slow as SDF forces were facing booby-traps "planted by the Takfiris to try to prevent the loss of the city."

The SDF has faced fierce resistance from ISIL since launching the assault to take Manbij on May 31. It managed to encircle the city earlier this month but its advance slowed as ISIL fought back, including with almost daily suicide bombings.

The terrorists have held the city since 2014, the year ISIL seized control of large parts of Syria and neighboring Iraq and declared its so-called "caliphate".

Manbij, which had population of about 120,000 before the start of Syria's civil war in 2011, is a key stop on ISIL's supply route from the Turkish border to its de facto Syrian capital of Raqa.