ISTANBUL/BEIRUT (Reuters) - Turkish-backed rebels have seized the center of al-Bab town from Islamic State, Turkish state media and rebels said on Thursday, in a boost to Ankara’s drive to defeat the militant group in northern Syria.

FILE PHOTO - Free Syrian Army fighters carry their weapons as they stand on the outskirts of the northern Syrian town of al-Bab, Syria February 4, 2017. REUTERS/Khalil Ashawi /File photo

Turkey launched its “Operation Euphrates Shield” in August in an effort to push Islamic State from its border and stop the advance of a Syrian Kurdish militia.

Taking control of al-Bab, an Islamic State stronghold 30 km (20 miles) from the Turkish border, would deepen Turkish influence in an area of Syria where it has effectively created a buffer zone and would allow the Ankara-backed forces to press on towards Raqqa, Islamic State’s de facto capital in Syria.

The Free Syrian Army (FSA) fighters, a loose coalition of Syrian Arabs and Turkmen, have been attacking al-Bab since December, aided by Turkish warplanes, tanks and special forces.

Turkey’s state-run Anadolu Agency, citing its correspondent in al-Bab, said the rebels had seized control of the town center and were now clearing mines and explosive devices laid by the jihadists. Some 1,900 square kilometers (734 square miles) in northern Syria has now been cleared of militant groups, it said.

A war monitor, the Britain-based Syrian Observatory for Human Rights, said later on Thursday that Euphrates Shield forces had taken full control of al-Bab and of two neighboring towns, Qabasin and al-Bezah.

“We had reached the city center yesterday but there was a suicide attack so we had to withdraw a little bit. And today we attacked again. I can say that 85-90 percent of the city is under control,” a fighter from the Sultan Murad Brigade who is in al-Bab told Reuters by telephone.

“They have dug tunnels all under Bab and those who have remained are all suicide bombers. The whole of the city is mined. I can say that every meter is mined.”

Another fighter with an FSA group contacted via a social networking site said there was “complete calm” in al-Bab. The fighter said he was speaking from the city center.

Turkish Defense Minister Fikri Isik told Anadolu the rebels had entered the town center and that most of the town itself was now under their control.

However, the Syrian Observatory for Human Rights monitoring group said that more than half of al-Bab was still under IS control, and that battles continued.

There was no immediate comment from the Turkish military.

STILL FIGHTING

Earlier, a Turkey-based rebel official from a group previously involved in fighting in Aleppo province said the rebels had taken control of al-Bab, although pockets of IS militants were still fighting.

“There has been cleaning up of the last remaining areas of (IS) control, and there were street battles,” Zakaria Malahifji of the Fastaqim faction told Reuters, adding that all the strategic areas of the city had been captured.

Turkish officials have repeatedly said that the al-Bab operation was taking longer than anticipated because of numbers of civilians still in the town and the care being taken not to harm them. It dropped leaflets on the town as long ago as December urging civilians to seek shelter

While Euphrates Shield has been largely focused so far on combating Islamic State, Ankara is also determined to prevent the Kurdish YPG militia, which it considers a terrorist group, from linking the cantons it controls along the Turkish border.

Turkey fears that advances by the YPG could enflame a Kurdish insurgency at home.

President Tayyip Erdogan has said the next target for the Turkish offensive should be Raqqa but that the YPG should not be involved.