Boko Haram Islamists have recaptured the strategic town of Marte in northeastern Nigeria's restive Borno state, a regional official said early on Saturday.

"It is sad as we have been made to understand that Marte has today completely fallen under the control of the insurgents, which to us is a very huge setback," said Mustapha Zannah, vice governor of the Borno state.

The town, located along a strategic trading route between Nigeria and neighbouring Cameroon and Chad, has traded hands between the jihadists and government troops numerous times since 2013.

A regional military coalition of Nigeria, Niger, Chad and Cameroon has claimed a series of major victories against Boko Haram since launching sweeping offensives against the jihadists in February.

Boko Haram's six-year insurgency has claimed some 15,000 lives and displaced about 1.5 million people.