A Saudi soldier was killed by gunmen late on Tuesday in the Eastern city of Qatif, in an incident the interior ministry said was carried out by "terrorist elements".
The security patrol came under fire upon approaching a suspicious vehicle, the statement carried by state news agency SPA, adding that the gunmen fled the area.
Eastern Province is home to much of Saudi Arabia's oil production as well as many Shi'ite Muslims, who form a minority in the conservative Sunni Muslim kingdom. Qatif has been the focal point of Shi'ite unrest since protests in early 2011 calling for an end to discrimination, which Saudi Arabia denies.
There was no immediate claim of responsibility for the attack. Shi'ite militants angry at what they say is repression of their community have attacked security forces in Eastern province in the past.
The ISIL militant group, which controls territory in Syria and Iraq, has also claimed attacks on Saudi security forces as well as deadly bombings and shootings that target the kingdom's Shi'ites.
In the past week, Saudi security forces killed two wanted men in separate incidents in Eastern province.
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