Backed force advances in fight for IS Syria bastion

An worldwide coalition pounded Raqa with air strikes Thursday, with a monitor saying at least 17 civilians had been killed in the bombardment as US-backed fighters pushed further into the Islamic State group s Syrian bastion.

The U.S. -backed Syrian Democratic Forces launched their attack on Raqqa earlier this week and U.S. -led coalition airstrikes have intensified since then.

He said SDF forces were also advancing on the northern front outside the city, and had repelled an attack by IS fighters as they pushed towards the city limits from the west.

The government advance coincides with the invigorated push by the USA -backed Syrian Democratic Forces (SDF) toward Raqqa's provincial capital. The war monitor, the Syrian Observatory for Human Rights, said the SDF had taken Mishlab and more than half of Sabahia.

He said that Syrian government troops had secured territorial gains in the southern Suwayda province near the Jordanian border, but encountered resistance from the USA -led coalition.

But the force has struggled to advance from the city's north, where IS holds a military complex known as Division 17.

It said heavy clashes continued to rock other parts of the neighbourhood, where at least 15 civilians were killed Thursday night in air strikes that hit an internet cafe.

"Hundreds" of US military personnel are taking part in the Raqqa offensive, according to the Pentagon, which said Thursday it believed up to 2,500 ISIS fighters were still holed up in Raqqa.

The UN children's agency UNICEF warned Friday that "an estimated 40,000 children remain trapped in risky conditions in Raqa city".

"Many are caught in the crossfire", UNICEF official Geert Cappelaere said, urging all parties to give safe passage to those who want to leave. One of the dead was an activist with the group, it added.

Lt. Gen Steve Townsend, the coalition's commanding general, said the twin offensives in Mosul and Raqqa could deal an important blow to Islamic State recruiting.

"As a matter of policy the Coalition does not discuss the employment of specific weapons and munition usage; however, in accordance with the law of armed conflict white phosphorus rounds are used for screening, obscuring, and marking in a way that fully considers the possible incidental effects on civilians and civilian structures", the spokesperson said. Worldwide law prohibits its use in civilian areas because of its indiscriminate effects, from starting fires to causing excruciating burns for bystanders, according to Human Rights Watch, which said it was investigating the allegations.