Tension is growing in the area, one of the main centres of the Shi'ite community in majority Sunni Muslim kingdom
A Saudi policeman was shot dead and three were wounded during a raid which devolved into a gun battle in the eastern Saudi city of Awamiya on Sunday, state news agency SPA said.
"An exchange of fire led to the injury of Corporal Majid bin Turki al-Qahtani, and his death after being taken to hospital - may God have mercy on him and accept him as a martyrs - and wounded three security men, a citizen, and a (foreign) resident," with moderate wounds, SPA said.
The agency said forces undertook the search against "terrorist elements" and retrieved automatic weapons, pistols and communication equipment. It added that four Saudis were arrested after the firefight for targeting the officers.
Tension is growing in the country's oil-rich Eastern province, one of the main centres of the Shi'ite community in majority Sunni Muslim Saudi Arabia, as neighbouring Yemen, Iraq and Syria contend with violent sectarian conflict.
Some leading clerics of Saudi Arabia's official Wahhabi school of Sunni Islam view Shi'ites as heretics.
Saudi security forces killed four militants in a clash in the Awamiya region in December, and it has been the focal point of unrest among Saudi Shi'ites since protests in early 2011 calling for an end to discrimination against the minority sect and for democratic reforms in the Sunni monarchy.
More than 20 people have been killed in the unrest since then, most of them local people shot in incidents that police have described as exchanges of fire. Shi'ite rights activists say some of those killed were shot dead while peacefully protesting, which the government denies.