Pressure mounts on IS

Pressure mounted on the Islamic State group yesterday as a Kurdish-Arab alliance launched a major assault north of the jihadists' Syrian bastion of Raqa and Iraqi forces advanced on their stronghold of Fallujah.

The twin offensives marked some of the most serious ground efforts against IS since the group declared its self-styled "caliphate" straddling the Syrian-Iraqi border in 2014.

Territory under IS control has been steadily shrinking for months but -- in a sign of its continued ability to mount attacks -- the group has carried out a wave of violence including bombings in the Syrian regime's coastal heartland Monday that killed more than 160 people.

Yesterday, Kurdish and Arab fighters announced their largest offensive to date against IS territory north of Raqa, the group's de facto Syrian capital.

The Syrian Democratic Forces -- a seven-month-old alliance between Kurdish and Arab forces -- said it would push IS from the province's north and secure other areas already seized from the jihadists.

Its statement, posted on Twitter, made no mention of the provincial capital, Raqa city.

Baghdad-based US military spokesman Colonel Steve Warren confirmed the assault, saying: "The SDF have begun operations to clear the northern countryside, so this is putting pressure on Raqa."

The US military will conduct air strikes in support of the "several thousand" SDF fighters, some of whom have been trained and equipped by the United States, he said.

If Raqa falls, "it's the beginning of the end of their caliphate," Warren said.

Just before the SDF announcement, Russia said it would be ready to coordinate with both Washington and the SDF in an offensive for Raqa.

The US rejected a Russian proposal last week to carry out joint air operations against jihadist groups in Syria.

The anti-IS coalition headed by Washington has set its sights on Raqa in Syria, as well as Fallujah -- and eventually IS's main bastion of Mosul -- in Iraq.

In Iraq, forces closed in on Fallujah after capturing the nearby town of Garma and cutting IS off from one of its last support areas.

The Hashed al-Shaabi umbrella paramilitary organisation, dominated by Tehran-backed Shia militias that are heavily involved in the operation, said ground was also gained south of Fallujah.

With forces converging on the city, concerns grew that the estimated 50,000 civilians believed to still be inside had nowhere to go.

A Fallujah resident reached by telephone told AFP there was heavy shelling on the northern edge of the city yesterday.

Iraqi and US-led coalition aircraft have been pounding Fallujah and its surroundings in recent days to support the operation.