BEIRUT — US-backed fighters in Syria on Thursday closed off all major roads leading to the northern Syrian town of Manbij, a stronghold of the Islamic State group, and had it nearly surrounded, officials and opposition activists said.
The town is one of the largest IS-held urban areas in northern Aleppo province. It’s also a waypoint on an Islamic State supply line between the Turkish border and the extremists’ de facto capital, Raqqa. If the US-backed Syria Democratic Forces capture Manbij, it would be the extremists’ biggest defeat in Syria since government forces took the central historic town of Palmyra in March.
The US Central Command said the Manbij operation is part of the ‘‘moderate Syrian opposition’’ efforts to clear areas along the border with Turkey from IS. Members of the American and French military have been advising forces fighting IS in northern Syria.
A statement by the Military Council of the City of Manbij, which is part of the SDF, said that all roads from the east, north and south have been cut. The group said they are now close enough to target IS inside the town, but they are holding off storming Manbij to avoid civilian casualties.
The Britain-based Syrian Observatory for Human Rights said SDF fighters are about a half-mile from the last main road linking Manbij with the city of Aleppo. Since the SDF offensive began on May 31, the Observatory says that 132 IS militants, 21 SDF fighters and 37 civilians have been killed there.
Mustafa Bali, a Syrian journalist who visited the front lines in Manbij on Thursday, told The Associated Press that the extremists don’t appear to be preparing to withdraw from Manbij as they had from other areas. He added that on Wednesday, black clouds covered the city as IS set tires alight to apparently obscure visibility inside Manbij and prevent airstrikes by the US-led coalition planes flying overhead.
‘‘Daesh is preparing for a battle inside the city,’’ Bali said, using an Arabic acronym to refer to Islamic State. SDF official Nasser Haj Mansour said on Wednesday that some 15,000 civilians had fled Manbij.
In its statement, the US Central Command also said that the US-led coalition has conducted 105 strikes in support of the battle to liberate Manbij. It added that the ‘‘Syrian Arab Coalition is leading the operation and will be responsible for securing Manbij once it is freed’’ — an apparent attempt to calm the town’s Arab residents who fear that Kurdish fighters, who are predominant in the SDF, will also enter their town.
The statement said coalition advisers are assisting the fighters in the battles ‘‘with command and control from nodes located behind the forward line of friendly forces.’’
In France, an official confirmed that French special forces are offering training and giving advice to SDF fighters. The official with the French Defense Ministry, who spoke on condition of anonymity because he was not authorized to speak on the record, said its forces are with SDF fighters who are fighting against IS. He didn’t provide other details.
In an interview last week, French Defense Minister Jean-Yves Le Drian said French forces were participating. ‘‘We are helping with arms, we are helping with aerial support, we are helping with advice.’’
