The Iran-backed Huthis have escalated attacks on the kingdom, while they step up an offensive to seize the Saudi-backed Yemeni government's last northern stronghold of Marib.

The Saudi-led military coalition thwarted a "Huthi ballistic missile attack" targeting Riyadh, the state-run Ekhbariya television said, without specifying the number of missiles intercepted.

AFP correspondents and residents of the Saudi capital reported hearing multiple loud explosions.

The rebels did not immediately claim responsibility for the attack, but they have previously targeted Riyadh with missiles and drones.

The assault comes as Saudi Arabia hosts a Formula E championship on the outskirts of Riyadh, which state media said was attended by de facto ruler Crown Prince Mohammed bin Salman.

The Huthis have escalated cross-border attacks on the kingdom even after the United States moved to delist the rebels as terrorists and stepped up efforts to de-escalate the six-year conflict.

The designation, imposed by the previous US administration of Donald Trump, had been widely criticised by aid organisations, who warned it would hamper their efforts to alleviate a humanitarian crisis in Yemen.

Current US President Joe Biden has halted support to Saudi offensive operations in Yemen's war, which he called a "catastrophe" that "has to end". But he has also reiterated US support for Saudi Arabia in defending its territory.

Alongside the cross-border attacks, the Huthis are pressing ahead with a deadly offensive to seize the Yemeni government stronghold of Marib, where some of the country's richest oil fields are found.

Years of bombings have failed to shake the rebels' hold on the capital Sanaa, and they have steadily expanded their reach in the country's north.

The grinding conflict has claimed tens of thousands of lives and displaced millions, according to international organisations, sparking what the UN calls the world's worst humanitarian crisis.