Clashes between Turkish-backed Syrian rebels and ISIS militants intensified around the northern Syrian town of al-Bab.

Fourteen Turkish soldiers were killed and 33 wounded in clashes with ISIS extremists – 138 of whom were killed – in Syria on Wednesday in the military’s highest single day toll of its four-month campaign inside the country.

The fighting came as Turkey and allied pro-Ankara Syria rebels faced increasing resistance from the extremists in a battle to take a key town ISIS-held town of al-Bab, 25 kilometres (15 miles) from the Turkish border.

The toll, the heaviest single day loss for the Turkish army in its Syria operation that started in August, came in fighting with extremists that included three suicide car bomb attacks, the army said in a statement quoted by Turkish media.

Four soldiers were killed in attacks earlier in the day, the army had previously announced. The other 10 were killed later Wednesday.

Six of the 33 wounded were said to be in a serious condition.

The fierce fighting erupted as Turkish officials said the army was entering into a key phase in the fight for al-Bab.

“Once this area has been seized, Daesh’s dominance of al-Bab will to a large extent be broken,” it said in a statement, using an Arabic acronym for the group. ISIS was using suicide bombers and vehicle-borne explosives intensively, it added.

Turkey’s military was pressing on with the operation after its foreign minister and his Russian and Iranian counterparts said in Moscow on Tuesday that they were ready to help broker a deal to end Syria’s almost six-year-old war.

The talks came as Syrian government forces neared their biggest victory in the conflict, closing in on the last rebel enclave in the long-embattled city of Aleppo.

Around 20 Turkish soldiers have been killed in the course of the “Euphrates Shield” operation, launched nearly four months ago, to push ISIS and a Kurdish militia away from Syria’s border with Turkey.

In the latest clashes, four Turkish soldiers were killed and 15 soldiers wounded, some of them seriously, the military said.

“Currently clashes are continuing intensively in the area,” the military statement said, describing the hospital area, on the slope of a hill overlooking al-Bab, as having long been used by ISIS as a weapons and ammunition store.

Turkish air strikes on Wednesday morning destroyed 24 ISIS targets and killed more than 40 militants, according to estimates by the army. It added that some 15 extremists had been killed in the previous 24 hours.

Four Turkish soldiers were slightly wounded when the vehicle they were traveling in was damaged by a roadside blast.

[vuukle]