SANAA - Yemeni Houthi rebels said they fired a ballistic missile at a Saudi military camp in the southwest of Saudi Arabia, the group's al-Masirah TV reported on Monday.

"The missile hit the camp in Sudais area in Najran, Saudi border city, killing dozens," the television quoted a statement from the group's military spokesman Yahya Sarea as saying.

It was the sixth attack by Yemeni Houthi militias against Saudi Arabia in less than 24 hours.

The attack was announced by the Houthi group just an hour after they claimed multiple drone attacks on a military site in the Saudi capital Riyadh.

There has been no comment yet from Saudi side on the attack.

Houthis have recently stepped up missile and drone attacks on Saudi Arabia, but most of the attacks were intercepted by the kingdom's air defences.

Saudi Arabia has been leading an Arab military coalition against Iran-backed Houthis in Yemen for more than four years in support of the exiled internationally-recognized government of Yemeni President Abd-Rabbu Mansour Hadi.