Flames, smoke at Aramco facility south of Saudi capital: AFP

Flames and smoke were seen rising from a facility belonging to Saudi oil giant Aramco south of the kingdom's capital Riyadh on Saturday, an AFP journalist said.

The circumstances remained unclear but in recent weeks Aramco, majority-owned by the Saudi state, has come under attack from the Houthi group targeting the kingdom as part of the war in Yemen where Riyadh is backing the internationally recognised government.

The journalist reported seeing fire engines attempting to extinguish a blaze at the energy giant's Riyadh refinery, located south of the capital, while ambulances and police vehicles were stationed near the facility.

Both the Houthis and Saudi authorities had yet to comment on the incident.

Aramco remains the flagship company of the Saudi economy and one of the largest firms in the world by market capitalisation.

Last month, the Houthis said that they launched strikes targeting "sensitive sites" in Riyadh and Aramco facilities in the kingdom's port city of Yanbu.

In August they also targeted an airport and a facility belonging to Aramco in Saudi Arabia's southern Najran region.

In July the Houthis announced a maritime blockade of Saudi Arabia, hitting Saudi tankers in the Red Sea and raising questions about Riyadh's continued ability to deliver vast quantities of crude to international markets.

Yemen, one of the world's poorest nations, has been embroiled in more than a decade of civil war.

On Saturday loud explosions were heard in the Yemeni capital of Sanaa, AFP correspondents in the city said, while the Houthis reported airstrikes in the area by Saudi-backed government forces.