Yemen's Houthis said on Thursday they had attacked a pumping station on Saudi Arabia's East-West oil pipeline and an oil facility in Yanbu on the kingdom's Red Sea coast, in a sharp escalation of hostilities between the Iran-aligned group and Riyadh.

Saudi Arabia did not immediately respond to a request for comment, and the Houthis did not say on which day the attacks were carried out. There was no immediate independent confirmation of damage.

Houthi military spokesman Yahya Saree said the group had carried out a drone strike on Pumping Station No. 11 in the Yanbu area and had also targeted Riyadh's King Khalid International Airport with three cruise missiles. He said the group's operations were directed only at the kingdom's oil facilities and military bases.

A pipeline carrying 4% of world oil

The East-West Pipeline matters far beyond Saudi Arabia. With the war disrupting oil flows through the Strait of Hormuz, Riyadh has rerouted about 4 million barrels of crude a day through the pipeline to Yanbu, equivalent to about 4% of global supply.

The pipeline has spared Saudi Arabia, the world's biggest oil exporter, from the worst effects of the wartime shutdown of the Strait of Hormuz, which has crippled exports from its neighbours. A successful attack on it would therefore strike at the workaround keeping Gulf oil moving.

The group has been firing ballistic missiles and drones at Saudi airports, ports and oil installations in recent weeks, turning the US ally into a pressure point in a war that began in February, when the US and Israel attacked Iran.

Mecca claim denied

Separately on Thursday, the Houthi spokesman denied that the group had targeted Mecca with two ballistic missiles that Saudi Arabia's civil defence said had been intercepted and destroyed on Wednesday, with debris falling in the Mecca region, including in Sabuhah village.

The Houthis have repeatedly denied targeting Mecca and Medina, Islam's two holiest cities, rejecting previous Saudi-led coalition accusations that they launched drones towards them. Saudi-led coalition forces said they had intercepted three cruise missiles heading towards Riyadh, along with drones launched towards Mecca and other parts of southern Saudi Arabia.

Saudi Arabia's Civil Defence Authority condemned the alleged attacks in a statement issued early on Thursday, describing them as a violation of international humanitarian law and accusing the Houthis of targeting civilian infrastructure.

Fighting intensifies inside Yemen

The alleged attacks on Saudi Arabia came as hostilities escalated inside Yemen between forces backed by Riyadh and Houthi fighters. Yemen's army spokesman, Majed Abdullah al-Nuzaili, said at least 138 Houthi fighters had been killed or wounded during hundreds of military operations.

The World Health Organization has reported that casualties from the latest fighting reached 11,755 as of 8 November, including 2,098 people killed and 9,657 wounded, and that more than 320,000 people have been displaced since 1 August, including nearly 16,000 forced from their homes in the past week.

The Houthi military spokesman also said his forces had targeted a Saudi coalition military command and control centre in Aden's al-Buraiqa district with several ballistic missiles.

The escalation underlines how the conflict that began with the US-Israeli war on Iran in February has spread across the region, drawing in Saudi Arabia, Yemen and the shipping lanes of the Gulf.