The battle for the Islamic State group's de-facto Syria capital, Raqqa, has reached its "final stages," the US-backed force leading the assault said yesterday.
The Syrian Democratic Forces captured Raqqa's last grain silos from the militants in a surprise offensive on the city's northern neighbourhoods, mounted five days ago, the group said in a statement.
The US and its international coalition partners intensified their air raids on the militants' last remaining enclave, according to the Britain-based Syrian Observatory for Human Rights monitoring group.
The US also has hundreds of forces embedded with the Syrian fighters who provide artillery fire and other support.
Just 300 to 400 militants remain in Raqqa, according to the Observatory. The SDF control 90 per cent of the north Syrian city.
The Observatory accused the US-led coalition of killing more than 1,000 civilians in airstrikes on Raqqa since the SDF first entered the city in June.
The claim could not be independently verified.
The coalition has said repeatedly that it relies on the latest intelligence to minimize civilian casualties and strike only military targets.
Thousands of civilians remain trapped in the militants' enclave in the north of the city as human shields, according to the SDF.
Tens of thousands more have been displaced by the fighting since June, often to wind up in abject conditions in SDF-run camps near the Turkish border.
The predominantly Kurdish SDF say they want their own autonomous zone in a federated Syrian republic. They operate independently of the Damascus-based Syrian government, which is supported by Russia and Iran.
The government and its backers, and the SDF and the US, are at risk of clashing in the energy-rich eastern Syrian Deir el-Zour province, where both sides are rushing to grab territory from the embattled IS group.
The fighting there is largely concentrated around the provincial capital, also called Deir el-Zour, which lies 125 kilometres southeast of Raqqa, on the banks of the Euphrates River.
ISIS still controls broad swathes of eastern Syria and pockets of territory in neighbouring Iraq.