Saudi Arabia's air defences "intercepted" one of the missiles, while another crashed into a desert area south of Riyadh, coalition spokesman Turki al-Maliki said.

The missiles were "unquestionably" fired at the city "with the intention of hitting inhabited areas", he added.

Maliki blamed the attack on "militiamen and terrorists, vassals of Iran" who try to "threaten the security of Saudi Arabia, the region and the world".

Earlier on Wednesday Al-Ekhbariya state television said the country's air defences had intercepted the two missiles over Riyadh.

Two explosions were heard in the city, according to an AFP photographer.

Yemen's Huthi rebels quickly claimed responsibility for attacking "Riyadh Dry Port and other economic targets" in the Saudi capital with Burkan 2H ballistic missiles.

State-run Saudi Press Agency said the country's air defences hours earlier had also intercepted a ballistic missile targeting the southern city of Jizan.

The rebels also claimed the Jizan attack, via their Al-Masirah TV.

Maliki accused the Huthis of firing the missile from the northern Yemeni province of Saada and of "deliberately targeting populated civilian zones".

He said such "hostile action" proves the involvement of Iran in the Yemen conflict, repeating Riyadh's long-standing claim that regional rival Tehran is supplying the Huthis with ballistic missiles.

Saudi Arabia launched a military coalition in Yemen in 2015, aimed at rolling back the Huthis and restoring the internationally recognised government to power.

The Huthis have in recent months intensified missile attacks against Saudi Arabia.

The latest salvo came a day after US President Donald Trump exited the Iran nuclear agreement, which he criticised for excluding measures to curb Tehran's ballistic missile programme.