The Saudi-led coalition in Yemen said Saturday it had launched air strikes in support of pro-government forces battling a quickening Houthi rebel advance on the northern city of Marib.

The move came after a drone strike set a Riyadh oil refinery ablaze on Friday, in an attack claimed by the Houthis, as the rebels made major advances on Marib, seizing a strategic mountain.

The dawn strike on the refinery was the second major assault this month on Saudi energy installations, highlighting an escalation of Yemen's six-year conflict between the Saudi-backed Yemeni government and the Houthis, who are supported by Iran.

The European Union and Russia on Saturday joined Saudi ally the United States in condemning the attack and calling for an end to strikes on civilians and civilian infrastructure.

The air strikes launched by the coalition were designed to "thwart the Houthi militia's attempt to advance towards Marib in Al Kasrah", the official Saudi Press Agency (SPA) reported.

Al Kasrah is one of the lines of defence to the northwest of the city, which is the government's last remaining stronghold in the north and the capital of an oil-rich region.

The coalition, which entered the Yemen conflict in 2015 to defend the beleaguered government, said it had succeeded in destroying Houthi military equipment, including tanks, and inflicting "heavy losses".

Rebel-controlled Al Masirah television reported 38 air strikes across various parts of Marib, while a government official told AFP that the coalition had launched at least 20 strikes.

"At least 70 fighters were killed, including 22 from the government forces, and dozens were injured in clashes in the past 48 hours,” the source told AFP.

"The rebels launched a violent attack, including with tanks, in Al Kasrah and the attack was thwarted with aerial support from the coalition.”

The Houthis and the internationally recognised government have been locked in a power struggle since 2014, when the rebels overran the capital Sanaa. Since last month, the rebels have been pushing to seize Marib.

Loss of the city would be a huge blow for the Yemeni government, but would also threaten catastrophe for civilians, including at least one million displaced people sheltering in the region, many in desolate camps in the surrounding desert.

Despite the latest rebel advance, analysts say the city may not fall any time soon, given the coalition’s overwhelming firepower.

The rebels have been stepping up their cross-border attacks on Saudi Arabia despite a renewed push by the US administration of President Joe Biden to revive stalled peace talks.

Also on Saturday, the Saudi-led coalition said it had intercepted and destroyed a drone carrying explosives over the southern Saudi city of Khamis Mushait, SPA reported.

The coalition said it was taking "all operational measures to protect civilians and civilian infrastructure against terrorist attacks”, SPA added.

The European Union said "these aggressions must stop” in a statement Saturday condemning the strike on the Saudi oil refinery.

"The ongoing escalation in and around Yemen is undermining the efforts of the UN Special Envoy, delaying the prospect of a solution to the conflict, and increasing regional instability,” it added.

Russia also slammed the attack on Saturday, urging "all parties to the conflict in Yemen to strictly abide by the provisions of international humanitarian law” in a statement from the foreign ministry.

Moscow called on all sides to "immediately and completely abandon military operations that lead to the destruction of civilian infrastructure and casualties among the civilian population”.