Saudi Arabia's minority Shiite Muslims have staged protests in an eastern city, and four were shot dead, the Interior Ministry said Thursday.
The ministry statement did not say who fired the fatal shots in the city of Qatif, but a top official said security forces were fighting with demonstrators there.
Interior Ministry spokesman Maj. Gen. Mansour Al-Turki later told a news conference in Riyadh that authorities had to deal firmly with what he described as "rioters and hired elements" to restore security.
He said the "escalation of rioting" was systematic. Along with the four dead, he said nine were injured, including a woman.
The statement said two were killed Thursday during the funeral of one who had died earlier. Circumstances of the death of the fourth were not disclosed.
There has been a series of clashes between police and protesters in the country's Shiite-dominated eastern region, starting in the spring.
Though limited, protests in Sunni-dominated Saudi Arabia have been swiftly quelled. The monarchy apparently fears they could escalate as have others around the Arab world _ particularly in the neighboring island of Bahrain, where a Shiite majority is ruled by a Sunni king.
The Interior Ministry previously blamed what it described as "seditious" residents, saying they attacked security forces with guns and firebombs with the backing of a foreign enemy _ an apparent reference to Shiite power Iran.
The ministry statement Thursday said the deaths in the new unrest were the result of exchanges of fire since Monday with "unknown criminals," who it said fired on security checkpoints and vehicles from houses and alleyways.
"There was an escalation in the limited rioting. This escalation reached the level of threatening the lives of citizen and national security," Al-Turki told reporters.
He said investigation into who was behind the violence was under way.
There is a long history of discord between the kingdom's Sunni rulers and the Shiite minority concentrated in the east, Saudi Arabia's key oil-producing region. Shiites make up 10 percent of the kingdom's 23 million citizens and complain of discrimination, saying they are barred from key positions in the military and government and are not given a proportionate share of the country's wealth.