Syrian rebels who seized Jarablus from Islamic State group in a Turkey-backed operation on Wednesday have advanced up to 10 km (6 miles) south of the border town, rebel sources and a group monitoring the war said on Thursday.

The Syrian Observatory for Human Rights said Kurdish-backed forces opposed by Ankara had meanwhile gained up to 8 km (5 miles) of ground northwards, apparently seeking to pre-empt advances by the rebels.

The Turkey-supported operation aims to clear Islamic State group from the Syrian-Turkish frontier in an operation Ankara says is targeting both the militants and the Kurdish YPG militia, which is part of a U.S.-backed alliance also fighting Islamic State.

One of the rebel sources said the sides clashed at the village of al-Amarna, south of Jarablus, on Wednesday night as the insurgents advancing from the north met Kurdish-backed forces that had moved forwards from the south. The village was under rebel control on Thursday, the rebel source said.

The Observatory said light arms had been used.

A map forwarded by a second rebel source showed the Turkey-backed insurgents had advanced into Islamic State group-held areas both to the south of Jarablus and to the west along the Turkish frontier.

Turkey continued to oversee the operation, the rebel source added.