Clashes between rebels and Yemeni government fighters killed at least 111 in Marib in three days, pro-government sources said, following a renewed offensive by Huthi insurgents.

The fighting between Thursday and Sunday killed 29 pro-government personnel and at least 82 rebels, the pro-government sources told AFP.

"These areas witnessed fierce fighting amid artillery shelling from both sides and intense coalition air raids," a government military official said, referring to the Saudi-led military coalition that backs the government.

The Iran-allied Huthi insurgents escalated their efforts to seize Marib, the government's last stronghold in northern Yemen, in February, and the fighting has killed hundreds on both sides.

Control of the oil-rich region would strengthen the Huthis' bargaining position in peace talks, but the battle has also raised fears of a humanitarian catastrophe, as many Yemenis had fled to the area to escape fighting in other parts of the country.

Yemen's conflict flared in 2014 when the Huthis seized the capital Sanaa, prompting the Saudi-led intervention to prop up the government the following year. 

The fighting has killed tens of thousands and left some 80 percent of Yemenis dependent on aid, in what the UN calls the world's worst humanitarian crisis. 

The war has also displaced millions of people and left many on the brink of famine.