Saudi Arabia says it has shot down a ballistic missile fired by Yemeni rebels at the royal palace in Riyadh.

Mohammed Abdul-Salam, spokesman for the rebel Houthi movement in Yemen, said that a meeting of Saudi leaders at the Yamama Palace had been targeted - two hours before Saudi Arabia was due to announce the country's annual budget in a news conference expected to be attended by senior ministers.

Saudi state television said the missile was intercepted just south of the city and that no casualties or damage had been reported.

Witnesses in the capital have posted images on social media of smoke billowing into the air.

:: Yemen: The civil war and humanitarian crisis explained


Image: The attempted strike comes a month after Houthi rebels launched this missile aimed at Saudi King Khaled airport. Pic: Pro-Houthi Al Masirah TV

The attempted attack comes on the same day that the United Nations' human rights office confirmed the deaths of at least 136 civilians and other non-combatants in Yemen as a result of airstrikes carried out by the Saudi-led military coalition.

All of the killings occurred between 6 December and 16 December in four northern provinces, with Yemen's rebel-run TV station and a hospital among the targets.

Hundreds of world figures have urged the leaders of the United States, France and Britain to stop "stoking the flames of war" in Yemen, marking the 1,000th day of the war.

Image: Yemen is situated just south of Saudi Arabia

The statement, signed by 355 high-profile figures including Nobel peace laureates and religious leaders, states: "To prevent further catastrophe and famine, Yemen needs an immediate ceasefire; an end to all blockages on access for food, fuel and medical supplies; and investment in a new, inclusive peace process.

"If you don't want the burden of the lives of thousands more Yemeni children on your hands, then the time to act is now. Yemen can't wait any longer," it said.

Last month, the Houthi rebels launched a missile towards Riyadh's airport, which the US and Saudi Arabia said had been supplied by Iran.