Saudi Arabia was forced to extend the suspension of all flights to and from its main international airport in Riyadh on Monday after a further round of Houthi missile attacks caused more damage and left one dead.

The Gulf nation said it was taking the step after Houthi missiles killed 13 people on Saturday and left more than 300 injured. Saudi state TV broadcast CCTV footage that showed passengers deluged in smoke and falling masonry as they queued at the airport terminal to board a plane just as the Houthi missile struck.

King Khalid international airport was being kept closed to complete verification of the airport’s safety, the Saudi aviation authority said. Saudi Arabia’s military spokesperson also said further missile and drone threats had been detected.

The closure came as the country pressed ahead with the 25th WPC Energy Conference in Riyadh, hoping to project an image of normality.

The Saudi energy minister, Abdulaziz bin Salman, told the conference that “fear has no place in the Saudi lexicon”, emphasising that the resilience of the kingdom’s energy system and the determination of its people to confront crises.

An urgent review is under way as to how Houthi missiles are repeatedly penetrating badly stretched Saudi air defences. Schoolchildren and some office workers were advised to work from home. The Houthis have also targeted the city of Khamis Mushait, and the King Fahd international airport in Dammam.

Interceptor missiles are needed to protect government buildings, oil facilities and infrastructure hubs across a wide geographic area. The Houthis have vowed to attack Saudi airports across the country.

Houthi attacks since last month have targeted fuel tanks at Riyadh airport and its affiliated warehouses, destroying a parked Airbus A320 passenger plane and damaging at least five other aircraft.

The crown prince, Mohammed bin Salman, has not been seen in public since Tuesday last week, reflecting the pressure he is under to find a way out from a war that has intermittently dogged his leadership since 2014.

Inside Yemen, fighting continued in and around Taiz, the third city, and the most populous governorate, with Saudi air planes mounting eight separate strikes on any assembly of Houthi forces. As many as 60 fighters died on Sunday from both sides.

The governor of Taiz, Nabil Shamsan, on Sunday issued an urgent call to lift the Houthi siege and warned a shortage of medicines meant the city would soon run out of emergency surgical and intensive care services.

Overall the Houthis claimed the Saudis had mounted 124 raids through Sunday. The Saudis are seeking to locate Abdul-Malik al-Houthi, the reclusive leader of the Houthis, with rumours of his assassination repeatedly circulating, but Saudi Arabia does not seem to have contemporary intelligence on his precise whereabouts either in the capital Sana’a or in its stronghold of Saada.

On the diplomatic front, Abbas Araghchi, the Iranian foreign minister, spoke to the Saudi foreign minister, Faisal bin Farhan, on Sunday to see if there was a way in which Iran could act as a mediator between the Saudis and the Houthis, a group that Iran has trained and armed.

A meeting of the UN security council in New York on Tuesday is expected to debate a resolution calling the Houthis a foreign terrorist organisation.

The exiled leader of the Southern Transitional Council (STC), Aidarous al-Zubaidi, called for southern forces to fight on all fronts, and not just to defend the borders of the former South Yemen, in a move that is likely to be welcomed by Saudi Arabia as it supports the week-old call by the UN-recognised government to drive the Houthis out of the whole of Yemen, rather than just from the southern governorates.

The STC has a vision of an independent South Yemen that would recreate the separate state that existed between 1967 and 1990. The reunification of Yemen at the end of the cold war proved fragile and many southerners nurse longstanding grievances about the distribution of resources in the unified state.

The STC’s authority has been challenged by Abd al-Rahman al-Mahrami, the Salafist leader who commands the powerful Southern Giants Brigades.

Despite Araghchi’s efforts to reach out to the Saudis, Mohsen Rezaei, the more hardline secretary of Iran’s supreme national security council, claimed Iran was hitting five or six small vessels in the strait of Hormuz every night, explaining the vessels were being used by the Emirati military to move oil through the strait to larger tankers, thus breaching the blockade that Iran is seeking to maintain to push up oil prices and weaken Donald Trump.

Esmail Baghaei, the Iranian foreign ministry spokesperson, said Trump’s treatment of Volodymyr Zelenskyy, including his call for the Ukrainian president to stand aside showed the risks in dealing with Trump. He said: “Being an enemy of America can be dangerous, but being a friend of America is deadly. You can see for yourself what America’s friendship and enmity with its allies is like.”