Yemen's Houthis vowed on Wednesday to press on with attacks on airports and oil facilities in Saudi Arabia and said they struck the headquarters of oil giant Saudi Aramco, which was hit the day before.
The Iran-aligned group said it had launched ballistic missiles, cruise missiles and drones at Saudi Aramco facilities in the eastern city of Dhahran, King Khalid International Airport in Riyadh and an Aramco refinery in Riyadh, without saying when.
Saudi Arabia has faced widening Houthi strikes over the past week, including an attack on Riyadh airport on Saturday that killed 13 people.
The Houthis say they have been retaliating for the kingdom's backing of Yemeni government forces in the Yemen war that restarted last month, reignited by the US-Iran confrontation in the Gulf.
In a broad threat, the Houthis urged "international shipping companies," civilians and workers to evacuate airports and oil facilities, which they declared legitimate military targets.
Saudi-led forces say they intercept missile
The Saudi-led coalition said it had intercepted a ballistic missile fired by the Houthis towards Riyadh on Wednesday, and several loud booms were heard in the Saudi capital.
Saudi authorities earlier issued an alert for a possible aerial threat in Riyadh on Wednesday before the warning was lifted, a witness said. It wasn't immediately clear what caused the booms and there was no immediate comment from the authorities on their source.
The escalating conflict has dealt a blow to Saudi Crown Prince Mohammed bin Salman's ambitious plans to transform and diversify the Saudi economy and reduce its reliance on oil.
Saudi Aramco headquarters suffered extensive damage in Houthi attack, sources say
Oil giant Saudi Aramco's headquarters in Dhahran suffered extensive damage in an attack on Tuesday, with a fire spreading across several floors, three people with direct knowledge of the matter told Reuters.
Operations at the complex in eastern Saudi Arabia have continued normally but some employees have been asked to work from home, according to two of the people.
A fourth person said some functions had been shifted to global offices, adding that the fire was still burning into the early hours of Wednesday.
The facility hosts an operations center which helps the world's largest oil company oversee onshore and offshore oil rigs, refineries, export terminals and thousands of kilometers of pipeline.
Saudi Arabia's energy ministry said in a statement that Tuesday night's attack, which came as fighting between Yemen's Iran-allied Houthis and the kingdom intensified, had caused a limited fire.
Two of the sources said a fire started on the ninth floor of the south wing of the office block, and spread between the sixth and 10th floors.
Another source added that the top three floors of building, where the office of Aramco CEO Amin Nasser is located, were severely damaged, with part of the ceiling caved in and windows and doors blown out.
Aramco did not immediately reply to a Reuters request for comment.
Saudi Arabia to let executives attend 'Davos in the Desert' remotely after attacks
Saudi Arabia plans to make its flagship investment conference a hybrid event, giving executives the option to tune in remotely, after deadly weekend attacks on Riyadh airport prompted a rethink of travel to the kingdom, two people familiar with the matter said.
Some participants were still expected to fly in and could land at airstrips outside Riyadh, or even in neighboring Gulf states, and then drive to the capital to attend the Future Investment Initiative scheduled for later this month, one of the people said.
Earlier this month, organizers said the event would go ahead despite missile and drone attacks in the kingdom, which have struck key targets.
Asked for comment, an FII media representative pointed Reuters to a joint statement from the CEO and the chairman of the FII Institute sent before Saturday's attacks.
"As we prepare to welcome thousands of delegates to Riyadh for the exceptional 10th edition of the Future Investment Initiative, their safety and well-being remain our highest priority," CEO Maha Al Saud and Richard Attias, chairman of the executive committee, said.
On Monday, major oil bosses dropped out of an international conference in Riyadh which continued in person as planned at a convention center 10 km (6 miles) from Riyadh airport.
The move to a hybrid model for FII shows how Saudi Arabia is trying to maintain its push to attract global investment despite an escalating war with the Houthis that has challenged its efforts to turn Riyadh into a hub for global events. The kingdom has used the FII to showcase its plans to diversify its economy from oil and attract foreign investments.
The typical attendance of a large number of world leaders, corporate chieftains and financiers has led the event to be nicknamed "Davos in the desert," in a nod to the World Economic Forum's annual meeting in Switzerland.