Iran-backed Houthi rebels in Yemen launched a major attack on southwestern Saudi Arabia early Tuesday, targeting oil and other infrastructure in an escalation that risks widening the region’s conflicts and adding further pressure to crude prices.

Saudi-led forces vowed a resolute response, saying dozens of civilians had been injured. The Saudi Energy Ministry said the attacks had also caused fires at several facilities in the southern region, temporarily halting some operations.

The attacks mark a dramatic escalation in the Saudi-Houthi conflict, which flared up again in July, shortly after the US-Iran ceasefire unraveled, with Houthi missile attacks on Saudi oil facilities and tankers in an expansion of the Middle East war.

Oil prices on world markets rose more than 1% after Tuesday’s assault, as traders worried that Saudi oil exports through the Red Sea would be put at risk. Riyadh has rerouted most of its crude through the Red Sea port of Yanbu since the Strait of Hormuz has been effectively shut.

The global benchmark, Brent crude, was trading close to $99 per barrel.