Kurdish-Arab alliance push into Islamic State's Manbij bastion

The Syrian Democratic Forces [SDF] pierced into the Islamic State group's bastion city of Manbij on Thursday, more than a month after an operation was launched.

The US-backed alliance of Kurdish and Arab forces pushed into the city while supported with airstrikes from the 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 London-based group relies on a broad network of sources inside Syria to monitor the conflict.

There was "fierce street fighting in between buildings" and at least two SDF were killed when an explosion detonated in a residential building.

The latest breakthrough took place just hours after SDF fighters recaptured control of a village on the city's southwestern outskirts.

But progress was likely to be slow as SDF forces face booby-traps "planted by the extremists to try to prevent the loss of the city," Rahman said.

On Sunday, reports confirmed the SDF were almost two kilometres [1.2 miles] from the city centre of Manbij – a strategic supply route held by the Islamic State since 2014.

June figures showed at least 223 IS fighters and 28 SDF troops had been killed – as well as 41 civilians in coalition air raids – since the alliance offensive against Manbij began, according to the Observatory.

Manbij lies at the heart of the last stretch of IS-controlled territory along Turkey's border.

The siege has severed a key supply route for IS fighters, money and weapons from the Turkish border to the group's de facto Syrian capital of Raqqa city.

Syria's war has killed 280,000 people and displaced millions since it erupted with the brutal repression of anti-government protests in 2011.

IS has come under attack on several fronts since declaring a cross-border "caliphate" in Syria and Iraq in 2014.