Video: Fires engulf Saudi Arabia’s oil facilities after drone attacks.

Yemeni drones have hit two oil facilities of Saudi Arabia’s state oil giant Aramco in the country’s east, causing huge fires before dawn on Saturday.

A spokesman for Saudi Arabia’s interior ministry said in a statement that the attacks targeted two Aramco factories in Abqaiq and Khurais.

The statement did not identify the source of the attacks, but Yemen’s Houthi movement later claimed responsibility in an announcement on Al Masirah TV.

The movement’s military spokesman General Yahya Sare’e said 10 drones were deployed against the sites in Abqaiq and Khurais and pledged to widen the range of attacks on Saudi Arabia.

“This was one of the largest operations which our forces have carried out deep inside Saudi Arabia. It came after careful intelligence and cooperation with honorable and free people inside Saudi Arabia,” he said without elaboration.

Abqaiq, about 60 km (37 miles) southwest of Dhahran in Saudi Arabia’s Eastern Province, contains the world’s largest oil processing plant. Most Saudi oil exported from the Persian Gulf is processed there. Khurais, 250 km Dhahran, hosts a major Aramco oil field.

Home to much of Saudi Arabia’s oil production, Eastern Province has seen bouts of unrest since 2011 when protesters emboldened by the Arab Spring uprisings took to the streets.

Houthi fighters and their allies in Yemen’s army have carried out similar attacks in recent months in retaliation for the kingdom’s airstrikes in the impoverished nation and its crippling economic siege on the country.

The incident comes nearly a month after Saudi Aramco’s oil facilities in Shaybah, the kingdom’s largest strategic oil reserve near the UAE border, were targeted by Yemeni forces in a major drone attack.

Yemeni forces also launched a successful raid on a major pipeline spanning the kingdom in May.

Sare’e on Saturday pledged to widen the range of retaliatory attacks on Saudi Arabia.

“As long as the invasion and siege continues, we promise the Saudi establishment that our future operations will expand further and become more painful,” he said.

“There is no solution before the Saudi establishment other than halting attacks and putting an end to the siege,” Sare’e added.

The latest attacks also come as Saudi Arabia, the world’s top crude exporter, accelerates preparations for a much-anticipated initial public offering of Aramco.

The IPO forms the cornerstone of a program envisaged by de facto ruler Crown Prince Mohammed bin Salman, a son of King Salman, to replenish the kingdom once buoyant reserves which have dwindled in stride with falling oil prices and the protracted Yemen war.

The war has turned into a quagmire for Riyadh, with Yemeni forces increasingly using sophisticated weaponry in retaliatory attacks.

The UAE, Saudi Arabia’s most notable partner in the conflict, recently announced the gradual withdrawal of its troops from Yemen, largely because it believes the war has become “unwinnable”, according to US reports.

Yemeni forces regularly target positions inside Saudi Arabia in retaliation for the Saudi war, which began on March 2015 in an attempt to reinstall the country’s Riyadh-allied former regime and crush the popular Houthi Ansarullah movement.

The Western-backed military aggression, coupled with a naval blockade, has killed tens of thousands of Yemenis, destroyed the country’s infrastructure and led to a massive humanitarian crisis.