RIYADH (AFP) - Rare heavy downpours triggered flash floods in the Saudi capital on Sunday, forcing schools and universities to close and prompting calls by the authorities for citizens to remain indoors.

At least three people were reported missing, the state news agency SPA said, quoting civil defence spokesman, Colonel Abdullah al-Harithi.

He added that the authorities assisted dozens of people trapped by the floods, a rare phenomenon to hit the capital of the desert kingdom.

Heavy rains, accompanied by thunderstorms, have lashed Riyadh since late Saturday, triggering flash floods in several districts and cutting off power in the city's north, according to residents.

Col Harithi urged Riyadh citizens, estimated at more than five million people, to stay away from rivers, valleys and flooded tunnels, while the Education Ministry ordered schools and universities closed on Sunday.

Saudi Arabia, like other desert countries, rarely sees heavy rainfall and religious leaders often organise prayers for rain.

But in May last year around 20 people were killed in flooding that swept parts of Saudi Arabia, which had not experienced such a high volume of rainfall for 25 years.

And in 2011, around 10 people were killed in floods in the western city of Jeddah, where 123 people also perished in floods in 2009.

The inability of Jeddah's infrastructure to drain off flood waters and uncontrolled construction in and around the city were blamed at the time for the high number of victims.

The national weather service has warned of new storms expected Sunday in Riyadh and other parts of the kingdom.