There was no immediate comment from the Houthis.

On Sunday evening, Houthi military spokesman Yahya Sarea said in a video statement that its forces had launched missiles and drones at Riyadh and Dammam's airports, as well as two oil and gas facilities in Eastern Province, in response to 124 Saudi air strikes in Yemen over the previous 24 hours.

Sarea also reiterated a warning to airlines and passengers against using Saudi airports and airspace, except for journeys to and from the Islamic holy cities of Mecca and Medina.

The Houthis' forces, he vowed, would "continue their escalating operations deep inside Saudi, imposing the equation of 'a blockade for a blockade' and 'an escalation for an escalation' and targeting Saudi enemy reinforcements until the aggression ceases and the siege on our dear people is lifted".

Saturday's attack on Riyadh airport drew widespread international condemnation.

UN Secretary General António Guterres said he was "deeply shocked" and warned that attacks on civilians and civilian infrastructure were a violation of international law.

President Donald Trump said he would "make a decision" about the US joining Saudi Arabia's strikes on the Houthis. The US military is reportedly already providing intelligence and targeting support to the Saudi-led coalition.

Iran, which has repeatedly denied allegations that it provides weapons and training to the Houthis, said it was "deeply concerned" by the escalation and called for "dialogue and engagement" to resolve the situation.

Yemen has been devastated by a civil war that began in 2014, when the Houthis ousted the government from Sanaa. The conflict escalated in 2015, after the Saudi-led coalition intervened in an attempt to restore the government's rule.

A four-year-old informal ceasefire began to unravel in July, when the Houthis announced a "maritime embargo" against Saudi Arabia and began missile and drone attacks on Saudi airports, oil facilities and tankers in the Red Sea.

The Houthis said they were retaliating for what they call a Saudi blockade of ports and airports in their territory, as well as an air strike on Sanaa airport that they blamed on the kingdom. The Yemeni government claimed it was behind that strike, saying it was trying to prevent an unauthorised Iranian plane from landing.

Last month, the Houthis launched a surprise offensive along Yemen's south-western Red Sea coast and ousted pro-government forces from areas overlooking the Bab al-Mandab Strait, at the southern end of the Red Sea.

They said they posed no threat to international shipping passing through the waterway but that they would continue to target vessels from Saudi Arabia.

However, the seizure of the strait contributed to a surge in global oil prices because Saudi Arabia had been relying on the Red Sea for oil exports after the US and Israel's war with Iran effectively closed the Strait of Hormuz in the Gulf.

Last week, the Yemeni government announced the start of a new offensive aimed at retaking all territory held by the Houthis.

Pro-government forces said they were quickly able to retake areas around Bab al-Mandab with the help of intense Saudi air strikes, but the Houthis denied losing any territory.