More than 60 fighters were killed in clashes in Yemen Friday between Iran-backed Huthi rebels and government forces in the strategic northern province of Marib, government sources said.

Earlier this month, the Huthis resumed a push to capture Marib city, 120 kilometers east of the rebel-held capital Sanaa.

The city lies close to some of Yemen's richest oil fields and its capture would be major prize for the rebels.

Friday's dead included at least 27 pro-government forces and 34 Huthi rebels, a government source told AFP, adding it was the "most violent" day of clashes since fighting erupted on Feb 8.

The rebels moved into hills near a dam southwest of Marib city -- the last major toehold in the north for Yemen's Saudi-backed government -- with the area witnessing "the fiercest battles", according to the source.

A military source said that pro-government forces repelled the Huthi advances and reported heavy fighting that lasted "more than eight hours" in the Ablah region, south of Marib city.

There was loss of life on both sides, the military source added, without providing further details.

Yemeni military sources said air strikes targeted Huthi positions in several parts of the province.

The Huthi-run Al-Masirah TV channel reported 21 air strikes in different areas.

Yemen has been embroiled in a bloody power struggle since 2014 between its government, supported by Saudi Arabia, and Huthi rebels, who control most of the north.

The grinding conflict has claimed tens of thousands of lives and displaced millions, according to international organisations, sparking what the U.N. calls the world's worst humanitarian crisis.

The upsurge in violence this month has come shortly after Washington decided to remove the rebels from its list of terrorist groups, in order to ensure aid is unimpeded, and to pave the way to restart peace talks.

Observers say the Huthis want to capture Marib as leverage before entering into any negotiations.

The United Nations has warned of a potential humanitarian disaster if the fight for Marib continues, saying it has put "millions of civilians at risk".

Until early last year, life in Marib was relatively peaceful despite the civil war.

But as the front lines shift, and air raids by Saudi Arabia and its allies pound the area, there is new peril for civilians, with hundreds of thousands sheltering in camps in the surrounding desert that extends to the Saudi border.

Loyalist military officials told AFP earlier this month that the rebels had been using residents of one camp in the province's Sirwah district as "human shields".

The fighting shows no signs of abating despite heavy losses on both sides.