Forces close in on bastions

Syrian regime troops supported by Russia and US-backed fighters pressed twin offensives against the Islamic State group yesterday as pressure built on the jihadists' northern strongholds in the war-torn country.

The advance comes as 17 civilians -- nearly half of them children -- were killed in air raids on a popular market in eastern Syria on the first day of the holy Muslim month of Ramadan. The Syrian Observatory for Human Rights monitoring group blamed the attack on Russian or regime forces.

In northern Syria, IS fighters in the town of Tabqa are caught between Russian-backed regime forces advancing from the southwest and US-supported Kurdish and Arab fighters pushing in from the north.

The coincidence of the near-simultaneous attacks has raised speculation about possible coordination between the United States and Russia in the anti-IS fight.

The Syrian Democratic Forces -- led by the Kurdish People's Protection Units (YPG) -- last week launched an assault on Tabqa, its military base, and a nearby dam from the north of Raqa province.

They are slowly working their way through vast agricultural plains to reach the strategic locations and are still at least 60 kilometres north of Tabqa.

But after the government's latest advance yesterday, regime forces pushing north were closer to Tabqa than the SDF, the Syrian Observatory for Human Rights said.

Russian-backed government fighters are now within 24 kilometres (15 miles) of Lake Assad, the key reservoir in the Euphrates Valley contained by the Tabqa Dam, the Britain-based Observatory said.

"There is a joint operations room in Baghdad where the Iraqis and the Syrians are coordinating with the support of the Americans and the Russians," a source close to the regime said yesterday.

Russia last month floated a proposal for joint air strikes with the United States against jihadists in Syria, but the offer was swiftly rejected.

Two years after it shot to international infamy after declaring a fundamentalist "caliphate," IS is coming under mounting international pressure.

In Syria, besides the Raqa front, IS is also under attack by the Kurdish-led SDF in Aleppo province.

SDF fighters crossed the Euphrates near the border with Turkey and pushed west towards the jihadist-held Syrian city of Manbij.

Manbij lies at the heart of a pocket of IS-held territory along the border that US commanders regard as the principal entry point for foreign fighters and funds.

Both Manbij and Tabqa stand on a key supply route from the IS-held border town of Jarabulus to the jihadists in Raqa city.

Meanwhile,  a UN humanitarian agency yesterday said the Manbij has already displaced some 20,000 civilians and could uproot about 216,000 more if it continues.

Syrian fighters have surrounded Manbij from three sides as they press the onslaught against the jihadists near the Turkish border, a spokesman for the fighters said yesterday.

The US government estimates that IS has between 19,000 and 25,000 fighters in Syria and Iraq.