Ankara - Kurdish separatists killed seven Turkish soldiers in their deadliest assault in more than a year, as tensions between the US and Turkey heighten over Washington’s failure to withdraw American-backed Kurdish forces from a strategic Syrian town.

The roadside bomb attack on Thursday targeted an armoured army vehicle near the southeastern town of Gercus, according to the governor’s office in Batman province. It came after Turkish forces killed dozens of autonomy-seeking PKK militants over the past month in strikes on the group’s bases in southeastern Turkey and northern Iraq.

A flare in violence in the country’s Kurdish-dominated southeast has fuelled Turkey’s concerns over gains by US-backed Kurdish forces in neighbouring Syria, whom Ankara sees as an affiliate of the PKK. Ebrahim Kalin, a spokesman for President Recep Tayyip Erdogan, said a June deal for the pullout of Kurdish forces from the Syrian town of Manbij near Turkey’s border has been stalled by US inaction.

“This delay tactic is really starting to become a big problem,” Kalin told a news conference after Wednesday’s cabinet meeting. The US says there are few Kurdish forces left and that the remainder will leave as joint US-Turkish patrols of the town take hold.

Erdogan has repeatedly denounced the US for arming and training the Kurdish forces in Syria, calling it a menace to its own territorial integrity. Turkey has battled a Kurdish insurgency since the 1980s, and the frictions over the Syrian Kurdish forces compound other points of contention between the Nato allies.

Last month, Washington imposed sanctions on Turkey for not freeing US pastor Andrew Brunson, who is currently under house arrest after spending two years in jail over his alleged role in the failed 2016 attempt to depose Erdogan and his government.

Brunson denies any wrongdoing and is due to appear in court on October 12. The pastor’s lawyer petitioned Turkey’s top court for his release on Wednesday, adding that he would appeal to the European Court of Human Rights if Brunson isn’t freed. A Turkish appeals court refused to release the pastor last month, raising the prospect of further U.S. sanctions targeting Erdogan’s government and renewed market turmoil.