Yemen's Houthi militia said on Friday that they had attacked three Saudi oil refineries with nine bomb-laden drones.

"The attacks targeted the Aramco refineries in the Saudi cities of Riyadh, Jazan and Abha," Houthi military spokesman Yehya Sarea said in a statement aired by the Houthi-run al-Masirah TV.

The Houthi spokesman said the attacks were in response to what he claimed the Saudi "prevention of fuel ships from entering Yemen", vowing that his group would launch more attacks against Saudi Arabia.

Meanwhile, the Saudi-owned Al-Arabiya TV reported that "the Riyadh oil refinery was attacked on Thursday morning by a bomb-laden drone." It gave no further details.

The Iran-backed Houthi militia in Yemen has recently intensified cross-border drone and missile attacks against Saudi Arabia and the United Arab Emirates, which is part of the Saudi-led coalition backing the Yemeni government army. Most of such attacks were reportedly intercepted.

The escalation came after the militia has recently lost several strategic districts in the oil-rich provinces of Shabwa and Marib in central Yemen.

Yemen has been mired in a civil war since late 2014 when the Houthi militia seized control of several northern provinces and forced the internationally recognized government of President Abd-Rabbu Mansour Hadi out of the capital Sanaa.

The Saudi-led Arab coalition intervened in 2015 to support the Yemeni government.  ■