ISTANBUL (Reuters) - Turkey-backed rebels closed in on an Islamic State-held city in northern Syria on Friday, foreign minister Mevlut Cavusoglu said, with Turkish tanks and warplanes supporting the assault.

Rebel fighters gather during their advance towards the Islamic State-held city of al-Bab, northern Syria October 26, 2016. REUTERS/Khalil Ashawi

Hundreds of Arab and Turkmen fighters seized at least two villages west of al-Bab, the rebels said. The city is of strategic importance to Turkey, partly because Kurdish-dominated militias have also been trying to take it from the jihadists.

Turkish state media said late on Thursday that Ankara had sent 300 commandos to northern Syria to reinforce “Euphrates Shield”, the operation it launched three and a half months ago to push both Islamic State and Kurdish fighters back from the border.

“With our help, rebels have closed in on al-Bab,” Cavusoglu said in comments published on state broadcaster TRT’s website. “The operation here is expected to be completed soon.”

The Turkish army said its air strikes on Friday morning destroyed 34 Islamic State targets, including militant bases, shelters, vehicles mounted with guns and ammunition depots. It hit 10 targets the day before.

The military also said the rebels it backs had seized control of a highway between al-Bab and Manbij, a town some 50 km (30 miles) to the east.

“There is a major assault under way,” said a fighter with the Turkmen Sultan Murad brigade, speaking from inside Syria. “God willing we will break (IS) resistance this time. Very powerful troops were sent last night.”

The Syrian Observatory for Human Rights, which monitors the war through a network of sources in the country, confirmed there was an increased number of Turkish troops with the Euphrates Shield forces and that they were shelling heavily as they attempted to advance on al-Bab on Friday.

The Observatory said explosions triggered by Islamic State had caused casualties in a village close to al-Bab. It also said it had received information that 12 civilians were killed and 10 wounded by air strikes and bombardment by Turkish forces targeting the city.

The advance of the Turkish-backed forces potentially pits them against both Kurdish fighters and Syrian government forces in an increasingly complex battlefield.

Ankara is determined to prevent the Kurdish YPG militia, which it sees as a hostile force, from joining up cantons it controls along the Turkish border, fearing that would embolden Kurdish separatism at home.