Saudi Arabia's East-West oil pipeline, essential for bypassing the Strait of Hormuz, was attacked on Monday but operations were unaffected, official media said, as the kingdom and Yemen's Houthis trade strikes.

The Saudi Press Agency cited an official with the energy ministry as saying the pipeline was targeted in the Medina region in the west of the country, causing a "limited fire" that was extinguished.

"No injuries or fatalities were reported, and pipeline operations were unaffected," the report said.

The report did not say who was responsible, but Yemen's Iran-backed Houthis have repeatedly targeted Saudi oil infrastructure with drones and missiles.

The East-West pipeline, which enables the world's largest crude exporter to get its oil to market via the Red Sea, has taken on increased significance since the outbreak of the Middle East war as Iran seeks to choke off the main route for Gulf energy shipments through the Strait of Hormuz.

Earlier on Monday, Saudi authorities warned Riyadh residents of "a hostile aerial threat," a day after an attack on a skyscraper belonging to oil giant Aramco rattled the capital's business district.

"Please remain calm, stay indoors or in a safe place away from windows and doors, and follow the instructions of the Civil Defence," the alert said, before the warning was lifted minutes later.

Saudi Arabia has faced near-daily strikes from the Houthis for weeks after a truce in their long-running conflict unravelled in July.

On Monday evening, parents of students were alerted that schools in Riyadh were returning to online classes "as part of the ongoing precautionary measures".

Students had only been back in the classroom for two days following weeks of distance learning, and the message to parents did not say how long the new interval was expected to last.

The Houthis, who control large parts of Yemen, Saudi Arabia's impoverished southern neighbour, did not announce a fresh attack on Riyadh on Monday.

But they did report a Saudi strike on Hodeida airport on the Red Sea, which has long been out of use.

The Houthis' Almasirah television said the death toll from weekend Saudi strikes on a village in Sanaa province had climbed to 44, including more than 20 children.

On Sunday, the Houthis claimed attacks on Riyadh's business district, where witnesses said Aramco Tower was damaged.

Saudi authorities said the building suffered minor damage from falling shrapnel after an "attempted attack."

The Houthis have repeatedly targeted Aramco tankers, refineries, storage areas and the company's headquarters.

A Saudi-led coalition initially launched hostilities with the Houthis in March 2015, months after the group seized the capital Sanaa, forcing out Yemen's internationally recognised government. (AFP)



Edited by Cecil Wong