DUBAI: Three Shi'ite Muslims have been killed in eastern Saudi Arabia by what was reported as stray bullets fired by police, a Saudi activist said on Tuesday, raising tensions ahead of the Ashura holiday which has prompted clashes in the past.

Tawfiq al-Saif, an activist, told Reuters that the government was sending a team of investigators to the town of al-Qatif to investigate the deaths, which have angered Shi'ites in the oil-producing Eastern Province.

An Interior Ministry spokesman was not immediately available to comment on the report.

Saudi Arabia has escaped the popular protests that have swept three Arab heads of state from power this year, after the world's largest oil exporter offered a major package of incentives to its citizens.

But small-scale protests have taken place in the Eastern Province, where most of the kingdom's Shi'ite Muslims live. Activists said authorities responded by deploying armed riot police who had set up checkpoints.

The Eastern Province is the center of Saudi Arabia's oil production facilities and is connected by a 16-mile causeway to Bahrain, where Riyadh sent troops earlier this year to help the Sunni government end a Shi'ite uprising.

Saudi Shi'ites complain of systematic discrimination, which is denied by the authorities. King Abdullah has appointed members of the sect to advisory government bodies.

Saif said that a 19-year-old technical college student died on Sunday by what police had told his family was a stray bullet fired during a clash between security forces and unknown assailants.

On Monday, a girl was shot and killed and another young man, believed to be aged 24, was also shot dead during a march in al-Qatif. The activist said they were hit by stray bullets.

"Opening fire is a big mistake, especially as we approaching Ashura," Saif said, referring to the holiday when Shi'ite Muslims mark the anniversary of the slaying of Prophet Mohammad's grandson, Imam Hussein, in 680.

This year Ashura falls in early December.

Saif said that unlike provincial police, who had always held back from opening fire even during protest marches, shooting into the air had increased since riot police were deployed earlier this year in the province.

He said he hoped that an investigative team being sent by the Saudi government to look into the incidents would calm tensions.

"We expect this committee to work in a neutral way, to calm tensions. I hope it will calm spirits," he added.

Another activist, Mohammed al-Saeedi, said in a statement sent by email to Reuters that a peaceful march in al-Qatif on Monday ended when security forces opened fire on demonstrators.

Protesters marched in the evening in al-Qatif and in the nearby town of Awamiya, and one person was shot dead and at least 15 were wounded, including seven by gunfire, he said.

In separate incidents, a police vehicle ran over and injured a man in al-Qatif, while earlier this week, a young man was shot and critically wounded in Awamiya, near al-Qatif, Saif said. He added that there were unconfirmed reports the young man had died.

In early October the Interior Ministry said an unnamed foreign power, widely thought to mean Shi'ite-led Iran, had instigated an attack on a police station in the Eastern Province in which 14 people, including 11 members of the security forces, were injured.

Saudi officials say there are nearly one million Shi'ites out of a total population of 3.4 million in the Eastern Province, but an International Crisis Group report from 2005 said they number around 2 million and a 2008 U.S. diplomatic cable released by WikiLeaks said there are 1.5 million Shi'ites.

Shi'ites say they face discrimination in education and government jobs and that they are spoken of disparagingly in text books and by some Sunni officials and state-funded clerics.

They also complain of restrictions on setting up places of worship and marking Shi'ite holidays, and say that al-Qatif and the town of al-Ahsa receive less state funding than Sunni communities of equivalent size.

The Saudi government denies charges of discrimination.

King Abdullah has appointed three Shi'ites to the advisory Shura council and included Shi'ite leaders in "national dialogue" meetings where officials hear from representatives of different groups in society. AGENCIES