US-backed alliance pushes deeper into Islamic State Syria hub

US-backed Syrian fighters pushed further into the Islamic State group stronghold of Manbij Saturday, seizing a key road junction and grain silos overlooking the city, an activist group said.

The city lies close to the border with Turkey and is a key staging post on the extremists' supply line to areas under its control in eastern Syria and neighboring Iraq.

The US-backed Syrian Democratic Forces, which have thrust into Manbij after driving across the Euphrates River from the east, have encircled the city and are now closing in with the support of US-led coalition airstrikes.

The Kurdish-Arab coalition overran the Mills Roundabout in the south of the city Saturday after capturing nearby grain silos overnight, taking them significantly closer to the city centre, the Syrian Observatory for Human Rights said.

"The grain silos overlook more than half of Manbij. SDF fighters can climb to the top and monitor the city," said Observatory chief Rami Abdel Rahman.

The Raqqa Revolutionaries Brigades -- one of the Arab components of the Kurdish-dominated alliance -- confirmed that SDF forces had seized the silos and pushed into the city.

The Mills Roundabout lies less than two kilometers (one mile) from the city centre.

IS and the SDF are locked in intense street fighting as the extremists tried to defend their positions

The Observatory said IS and the SDF were locked in intense street fighting as the extremists tried to defend their positions.

Captured by the IS group in 2014, Manbij was a key transit point for foreign fighters and funds, as well as a trafficking hub for oil, antiquities and other plundered goods.

Across the frontier in Fallujah, security forces were poised to assault Jolan, the last neighbourhood still held by the militant group.

Tens of thousands of people fled the fighting, with many camped out in the open in the summer heat.

"Dozens of families are still without tents or any form of shelter inside the camps, living in miserable conditions. The majority are elderly people, women and children," the Norwegian Refugee Council said.

The SDF launched its offensive to take Manbij on May 31, driving across the Euphrates River from the east with military advice from some 200 US special forces troops.

IS has thrown large numbers of fighters into the battle, losing 463, according to the Observatory. The SDF has lost at least 89.

The extremists have taken some 900 Kurdish civilians hostage in areas under their control west of the city, according to the Observatory and Kurdish officials.

Manbij lies in the eastern plains of Aleppo province, which has become a battleground between an array of competing armed groups, including al-Qaeda, rebels and government forces, as well as the SDF and the IS group.