Two Saudi border guards have been killed in an ambush by gunmen in the south of the country, the interior ministry has said.
It said the attack happened in Najran district on the border with Yemen, without providing further details.
Unconfirmed reports say the gunmen were al-Qaeda militants, who had attempted to cross from Saudi Arabia into Yemen.
Saudi Arabia has been fighting al-Qaeda militants, who have used Yemen's lawlessness to set up bases there.
A number of suspects - both Saudi and Yemeni nationals - have been arrested in recent months by the Saudi authorities.