Islamic State (Isil) fighters have been waging a fierce counterattack with suicide bombers and armoured vehicles in the days since Donald Trump declared the jihadist group was “defeated” in Syria.

The Kurdish-led Syrian Democratic Forces (SDF) said Isil fighters were emboldened by the news of the US withdrawal and were fighting to retake the town of Hajin in Deir Ezzor just days after they were driven out.

“They got high morale from US decision to withdraw from Syria,” said Mustafa Bali, an SDF spokesman. “Isil is still strong in the region.”

The SDF said Saturday it was facing “a fierce and intense attack” by Isil fighters, who launched a wave of at least 17 suicide bombers at their lines followed by shelling and a barrage of rocket-propelled grenades.

Kurdish forces held the line and said they killed “dozens” of jihadist fighters with support by US airstrikes.

US and British officials fear, however, that the SDF will not be able to hold the territory it has taken from Isil, especially if it is forced to divert forces to the north in face of a threatened offensive by Turkey.