Two members of the Saudi security forces were killed on Wednesday in Saudi Arabia's restive eastern province after gunmen opened fire on their vehicle, an Interior Ministry spokesman quoted by state news agency SPA said.
"At one o'clock in the morning a security patrol in the province of Qatif came under fire from an unknown source", the spokesman said.
There was no immediate claim of responsibility for the attack which took place on the outskirts of the mostly Shi'ite Muslim town of Seihat.
The Sunni-ruled kingdom, the world's top oil exporter, has been hit by a spate of deadly shooting and bomb attacks in recent months, many of them claimed by Islamic State.
The militant group is bitterly opposed to Gulf Arab rulers and is seen as trying to stir up sectarian confrontation within Arabian peninsula states to bring about the overthrow of their ruling dynasties.
Qatif, an oil-rich province home to a large Shi'ite population, has witnessed protests for more rights in Saudi Arabia which is majority Sunni.
An Islamic State gunman killed five worshipers at a Shi'ite meeting hall in Seihat in October and a soldier was killed in the town of al-Jash in Qatif when his vehicle came under fire in July.
Saudi Shi'ites complain of discrimination in the birthplace of Islam, which follows the rigid Wahhabi Sunni school that views the minority sect as heretical.
The Saudi authorities deny the accusations and have said that those killed since protests began in early 2011 were shot in exchanges of fire.