The rare Saudi violence spread concerns about the world's largest oil producer, the evening before major protests and demonstrations have been planned.
The pro-Western monarchy has officially banned any protests and warned that security forces will take action against them.
The police fired percussion bombs, which was followed by gunfire, to disperse the protesting crowd, an anonymous witness said.
Philip Luther, a spok
Treasuries were up and oil prices spiked as news spread that Saudi police forces had opened fire on a crowd in the mainly Shiite eastern region of the Arab kingdom.