Yemen’s Houthi movement said on Saturday that it had launched 10 drones in an attack on oil facilities in Saudi Arabia, but there was no immediate confirmation from the Saudi authorities or the state oil giant, Aramco.

Speaking to Houthi-run television station, Al Masirah, a Houthi spokesman described the attack on Shaybah, close to the United Arab Emirates border, as the “biggest attack in the depths” of Saudi Arabia, the world’s top oil exporter, since the Saudi-led coalition intervened in Yemen in March 2015. The report did not say when the attack took place.

“We promise the Saudi regime and the powers of aggression bigger and wider operations if the aggression continues,” the spokesman was quoted as saying.

Video footage published by the semiofficial Iranian news agency Mehr showed what it said were drone attacks on Saudi facilities.

Warplanes from the Saudi-led coalition fired flares over the city of Aden, in southern Yemen, at dawn Saturday near camps occupied by southern separatist fighters who last weekend took over most of the Aden, a blow to the country’s internationally recognized government and to efforts by Saudi Arabia to put it back in control of all of Yemen.

The coalition renewed a call overnight for the separatist forces to withdraw from all sites they had recently captured in Aden. The coalition is battling the Iran-aligned Houthis to try to restore Yemen’s government, which the Houthi movement ousted from power in 2014. The war has been in military stalemate for years.

The separatist Southern Transitional Council said that its forces had already moved away from the presidential palace and the central bank, and were vacating other government institutions. They said the forces would not leave the government military camps that give them effective control of the city.

“We will not retreat, we will not budge, and planes will not scare us,” one of the brigades fighting as part of the southern separatists said in a statement issued on Saturday in response to the flares and low-flying warplanes.

The Houthis have escalated cross-border missile and drone attacks on Saudi Arabia in recent months. The claim of an oil field attack comes a day after the Houthis’ military spokesman said the group launched drone attacks on the international airport in Abha, Saudi Arabia, halting air traffic.

The Saudi authorities did not immediately comment on the reported attacks or disruption to traffic at the airport, which is about 95 miles from the Yemen border. Later Friday, Saudi state television cited the coalition as saying that a Houthi drone targeting the kingdom had been intercepted and downed. The airport was not mentioned.

On Saturday, Al Masirah, the Houthi channel, reported that ten drones had targeted Aramco’s Shaybah oil field and refinery.

In May, the Houthis claimed responsibility for a drone attack on two oil pumping stations in Saudi Arabia that caused a small fire, but it did not disrupt oil output or exports of crude and petroleum products.

The coalition has responded to the drone attacks with airstrikes on Houthi targets in Sanaa and other areas held by the group, which controls most large urban centers in Yemen.

The violence is complicating United Nations-led efforts to ease tensions in order to pave the way for talks to end the war, which has killed tens of thousands of people and pushed millions to the brink of famine.

The conflict is widely seen in the region as a proxy war between Saudi Arabia and Iran.

Saudi Arabia has accused Iran of supplying the Houthis with the missiles and drones used in attacks on Saudi cities, a charge both Iran and the group reject. The Houthis say they manufacture their own weapons and are fighting a corrupt system.

The Aden crisis has also exposed strains in the coalition that intervened in Yemen in 2015 to try to restore the Saudi-backed government. The separatists are backed by the United Arab Emirates, a member of the coalition.

-Reuters