Yemen's Houthi rebels said they launched a bomb-laden drone into Saudi Arabia, targeting an airport with a military base - an attack acknowledged by the kingdom. It was not clear if there were any injuries or what the extent of damage was.

 The Houthis' Almasirah satellite news channel said early on Tuesday the attack targeted the airport in Najran with a Qasef-2K drone, striking an "arms depot". Najran, 840km southwest of Riyadh, lies on the Saudi-Yemen border and has repeatedly been targeted by the Houthis.

A statement earlier on the state-run Saudi Press Agency quoted Saudi-led coalition spokesman Col. Turki al-Maliki as saying the Houthis "had tried to target" a civilian site in Najran, without elaborating.

Al-Maliki warned there would be a "strong deterrent" to such attacks and described the Houthis as the "terrorist militias of Iran".

The Yemen conflict has killed tens of thousands of people since a Saudi-led military coalition intervened with a devastating aerial bombardment campaign in support of the beleaguered government in March 2015, after the Houthis removed President Abd-Rabbu Mansour Hadi and forced him out of Sanaa, the capital.