Houthi rebels claim attacks on Saudi capital Riyadh

The Houthi rebels in Yemen say they have attacked "sensitive" sites in the Saudi capital Riyadh with missiles and drones, hours after flames and a large plume of smoke were seen near the city's main airport.

Saudi Arabia had sent alerts overnight warning of potential danger around Riyadh amid an escalation in attacks by the Houthis in the kingdom.

Reuters video and photographs showed a huge pillar of black smoke rising in the area, with the airport highway, main terminal building and other facilities in the foreground.

At one point in the video, flames were visible rising from behind what appeared to be fuel tanks.

The Houthi rebels did not specify what they had targeted in Riyadh but said they had also attacked an Aramco facility in the Red Sea city of Yanbu, a key Saudi oil export hub.

The Houthi movement said the operation came as a response to an attack in the Yemeni capital Sanaa.

There was no immediate comment from the Saudi government's media office in response to Reuters questions about the smoke and the overnight alerts, nor was there any immediate Saudi confirmation of the Houthi claims of attacks.

Saudi civil defence sent the alerts by phone overnight for potential danger of aerial attacks in Riyadh and the city of al-Kharj east of the capital, before issuing an all-clear on Saturday morning.

A Reuters journalist in Riyadh's Olaya area heard booms before the all-clear was sent.

The Houthis, who control the most populous parts of Yemen and much of the north, have been launching attacks against Saudi Arabia since declaring a naval blockade against the country in July, with strikes targeting Saudi vessels in the Red Sea.

The attacks have targeted Saudi cities, energy infrastructure and shipping, creating new threats to global oil supplies and putting at risk the main alternative Red Sea route for Gulf exports while traffic through the Strait of Hormuz remains blockaded.

On Friday Houthi military spokesman Yahya Saree said the group had foiled unspecified "criminal attempts" in the Yemeni capital Sanaa, blaming Saudi Arabia and vowing a response.

The Iran-aligned group, which seized Yemen's entire Red Sea coast in a lightning advance this month, said the Saudi Air Force has conducted hundreds of air strikes against it in recent days.