RIYADH (Reuters) - Saudi Arabia's King Salman on Tuesday ordered the Saudi Arabian National Guard, widely regarded as the kingdom's best equipped military ground force, to take part in Riyadh's campaign against Iran-allied Houthi rebels in Yemen.

Military operations in the campaign have so far been carried out by the Royal Saudi Air Force and the Royal Saudi Land Forces, which answer to the Defence Ministry. The national guard is a separate military structure run by its own ministry.