A drone strike sparked a fire at a Riyadh oil refinery Friday, in an attack claimed by Yemen's Huthi rebels as the Iran-backed insurgents made major advances on the embattled Yemeni city of Marib.
The attack at dawn on the refinery is the second major assault this month on Saudi energy installations, highlighting a dangerous escalation of Yemen's six-year conflict between the Saudi-backed Yemeni government and the Iran-linked Huthis.
"The Riyadh oil refinery was attacked by drones, resulting in a fire that has been brought under control," the Saudi energy ministry said in a statement, adding that no casualties were reported and oil supplies were not disrupted.
Strongly condemning the "cowardly attack", the ministry said the drone strikes were not just an assault on the kingdom but the world economy and global energy security.
In a statement, the Huthi rebels claimed to have targeted energy giant Aramco in Riyadh on Friday with six drones in response to the "brutal aggression" of the Saudi-backed military coalition in Yemen.
The rebels are stepping up cross-border attacks on the kingdom despite a renewed push by the US administration of President Joe Biden to revive stalled peace talks.
The latest assault comes after Saudi Arabia earlier this month said it thwarted a missile and drone attack on Ras Tanura -- one of the world's biggest oil ports -- and Aramco facilities in Dhahran city in the kingdom's east. It reported no casualties or damage.
Friday's attack coincides with major Huthi advances on Marib city after the rebels took a strategic mountain in clashes that caused dozens of casualties on both sides, according to Yemeni government sources.
The Huthis "took control of Mount Hilan overlooking the city, after fighting which left dozens of dead and wounded on both sides," one of the sources told AFP.
"Marib is in danger," another source said, adding the loss of the mountain posed "a threat to Marib's first line of defence".