Nearly 80 rebels and pro-government troops have been killed in fighting for the strategic Yemeni city of Marib, military sources told AFP on Wednesday.

"Sixty Houthi rebels were killed  most of them in air strikes conducted in the last 24 hours -- while 18 pro-government troops were killed and dozens injured in clashes over the past 48 hours," a government military official said.

The figures were confirmed by other military sources, while the rebels rarely report casualty numbers.

Battles between Yemen's government, which is backed by a Saudi-led military coalition, and the Iran-allied Houthi rebels have intensified in recent days in the province of Marib, according to the military official, who spoke on condition of anonymity.

The fighting was concentrated in the north and west of the governorate.

The official said air strikes have also intensified.

The rebels themselves reported early on Wednesday that the coalition has launched at least 30 such strikes against them across Marib province.

"The Houthis launched last night a military offensive that continued into the early hours of Wednesday morning," the pro-government official said, adding loyalist troops were able to repel the insurgents despite a small advance on the northern front.

Yemen's internationally recognised government and the Houthis have been locked in war since 2014, when the insurgents seized the capital Sanaa.

In February, the Houthis escalated their efforts to seize Marib, the government's last northern stronghold in fighting that has killed hundreds on both sides.

Control of the oil-rich region would strengthen the Houthis' bargaining position in peace talks.