Authorities in Saudi Arabia say a police officer working on a traffic patrol has been shot dead in the kingdom's predominantly Shiite east amid continued unrest in neighboring Bahrain.

The Interior Ministry said the officer, identified as Faisal al-Harbi, was killed by unknown assailants early Friday morning in the city of Saihat. It said an investigation was ongoing.

The Sunni-ruled kingdom's Shiite east has been tense since the January execution of a prominent Shiite cleric. In recent weeks, an intensifying crackdown by the Sunni rulers of neighboring Bahrain has seen activists and Shiite leaders detained or forced into exile, exacerbating regional tensions.