Yemen's Houthis claimed Monday to have launched drone strikes against Saudi energy giant Aramco's facilities, amid an upsurge in fighting between the insurgents and the Riyadh-backed government in northern Yemen.

Neither Aramco or Saudi authorities immediately reported any attack.

Houthi spokesman Yahya Saree said in a statement carried by the rebels' Al Masirah television that the strikes took place overnight, in retaliation for the six-year military campaign led by Saudi Arabia in Yemen.

He said the Houthis had targeted Aramco refineries in the western Saudi city of Jeddah and in Jubail in the east, with 10 drones launched at dawn.

He also said the Houthis hit "sensitive military areas" in the southern cities of Khamis Mushait and Jizan, with five drones and two ballistic missiles.

On Sunday, the coalition said it had intercepted and destroyed Houthi drones targeting Khamis Mushait and Jizan.

The Iran-aligned rebels have struck Aramco facilities in the past, underscoring the vulnerability of Saudi Arabia's expensive and strategically vital oil infrastructure.

Last November, the rebels hit an Aramco plant in Jeddah with a Quds-2 missile, tearing a hole in an oil tank and triggering an explosion and fire, the company said.

The rebels' latest claim comes a day after at least 70 pro-government and Houthi fighters were killed in fierce fighting for Yemen's strategic northern city of Marib.

The Houthis have been trying to seize Marib, the capital of an oil-rich region and the government's last significant pocket of territory in the north, since February.

Meanwhile, the United Nations called on Monday on all parties involved in the conflict in Yemen to 'seize the opportunity' for a diplomatic solution as world powers held virtual talks.

UN Special Envoy for Yemen Martin Griffiths told reporters in Berlin ahead of the negotiations that peace efforts had reached a 'critical moment' after six years of fighting.

'This is a moment for responsible leadership,' he said, urging 'the parties to seize the opportunity that exists now and negotiate in good faith without preconditions'.

He was in Berlin at the invitation of German Foreign Minister Heiko Maas.

The meeting brings together high-ranking officials from the five permanent members of the UN Security Council plus Germany, Sweden, Kuwait, and the EU, a format established in 2019 for the Yemen conflict.

Griffiths said the dire humanitarian situation required an immediate response.

'In these six years Yemenis have increasingly and appallingly, lacked access to food and medicine' as well as basic services and freedom of movement, he said.

Children had faced over six years 'of being deprived of schooling, and being deprived of their future'.

'A generation has been lost,' he said.

Griffiths said a UN plan for a negotiated political settlement would first address 'critical humanitarian needs and build confidence between the parties'.

'We hope together that an agreement on all those humanitarian measures will create a conducive environment for the parties to move swiftly to inclusive peace talks under the auspices of the UN to sustainably and comprehensively end the conflict,' he said.

The UN was committed to a 'fair future' for the country's people which 'is deliverable, which is achievable, and which is long overdue', Griffiths said.

The conflict has killed tens of thousands of people and pushed millions to the brink of famine, in what the United Nations has described as the world's worst humanitarian crisis.