The European Union’s top diplomat has criticised Turkey over its military offensive in a northern Syrian town.

EU foreign policy chief Federica Mogherini called on Ankara to ensure that fighting eases in the conflict-torn country, saying: “I am worried about this.”

Ms Mogherini told reporters in Brussels that international efforts in Syria are supposed to be “aiming at de-escalating the military activities and not escalating them”.

She urged Turkey, Russia and Iran to guarantee that conflict “de-escalation zones” are established as promised, to “guarantee that that is what happens on the ground”.

Turkey’s president, Recep Tayyip Erdogan, announced on Sunday the capture of the town of Afrin, previously controlled by the Kurdish militia known as the People’s Defence Units, or YPG.

The call came as Turkey’s state-run news agency said a booby-trap bomb reportedly left by Syrian Kurdish fighters in the town of Afrin had killed 11 people — seven civilians and four Turkish-backed fighters.

Anadolu Agency said the explosion occurred late on Sunday in a four-storey building that Turkish-backed Syrian opposition forces were clearing for explosives.

Meanwhile, a Syria war monitoring group claimed Turkish-allied militiamen have been looting Afrin after the Turkish military and allied Syrian fighters seized control of it.

The Britain-based Syrian Observatory for Human Rights said the looting began on Sunday, after the Turkish and allied Syrian forces marched into the town centre and raised their flags there — nearly two months after the offensive on the Kurdish enclave started.

The troops faced little resistance from the Kurdish militia, which withdrew, vowing a “new phase” of guerrilla tactics against Turkish troops and their allied fighters.

The Observatory, which monitors Syria’s war through a network of activists on the ground, described extensive looting of shops, homes and cars in Afrin.