AMMAN (Reuters) - Islamic State said one of its suicide bombers killed some people on Monday at a military base in Syria’s Raqqa city, which is under control of a U.S.- backed and Kurdish-led militia.

The Syrian Democratic Forces (SDF), led by Kurds, said a militant blew himself up in a blast that killed one civilian and injured several of its fighters.

Though the SDF did not say where the blast took place, two Raqqa residents reached by Reuters said they heard an explosion in a central district of the city housing military offices.

The ultra hardline jihadist Islamic State’s (IS) claim of responsibility came in a statement by the affiliated Amaq news agency. It said the attack targeted a recruitment center in Raqqa and that 17 people were killed or wounded.

Amaq said the bomber, whom it named as Abu Abdullah al Shami, had first used his machine gun then detonated a vest.

The SDF also said earlier it had clashed with IS fighters who infiltrated through an old tunnel in the city near an outpost where their fighters were stationed.

The Kurdish-led alliance seized the city in Syria’s northeast from Islamic State with the help of U.S.-led air strikes in 2017.

Raqqa, which IS declared the capital of its self-proclaimed caliphate, was taken by the SDF six years into Syria’s civil war after a protracted battle that killed thousands of civilians and wrecked much of the city.

Rebuilding and restoring Raqqa, which was once home to more than 300,000 people, is proving a monumental task.

Since losing almost all the large swathes of territory it took in lightning offensives in Syria and Iraq in 2014-15, IS has returned to deadly hit-and-run attacks and ambushes.

Some people in Raqqa resent effective Kurdish control over the predominately Arab city, with many objecting to compulsory enlistment to its forces, heavy taxes on civilians and a tight security grip where dissent is not tolerated.