Saudi police opened fire Thursday to disperse a protest in the mainly Shiite, oil-producing east, leaving at least three people injured, as the government struggled to prevent a wave of unrest sweeping the Arab world from reaching the kingdom.
Word of the protest helped drive oil prices back up on international markets.
The rare violence raised concern about a crackdown ahead of planned protests after Friday prayers in different cities throughout the oil-rich kingdom. Violence there could reverberate through the world's markets because of the importance of Saudi oil exports.
Discord is common between authorities and the country's Shiites, who make up 10 percent of the kingdom's 23 million citizens. They have long complained of discrimination, saying they are barred from key positions in the military and government and are not given an equal share of the country's wealth.
Eyeing rising discontent across the Middle East and North Africa, Saudi authorities are increasingly determined to prevent the unrest from spreading to other cities.
Saudi security forces have deployed around the capital of Riyadh on the eve of planned protests calling for democratic reforms.
Witnesses reported Thursday seeing riot police and special forces with batons and tear gas canisters, particularly around shopping malls and main roads.
The pro-Western monarchy is concerned protests could open footholds for Shiite powerhouse Iran and has accused foreigners of stoking the protests, which are officially forbidden.
Despite the ban and a warning that security forces will act against them, protesters demanding the release of political prisoners took to the streets for a second day in the eastern city of Qatif.
Several hundred protesters, some wearing masks to avoid being identified, marched after dark asking for "Freedom for prisoners."
Police, who were lined up opposite the protesters, fired percussion bombs followed by gunfire, causing the crowd to scatter, a witness said, speaking on condition of anonymity for fear of government retaliation.
A spokesman for the Saudi Interior Ministry said police fired over the heads of the crowd after they attacked a police officer who was documenting the protest, and said two protesters and a police officer were injured.
The ministry said later two protesters received hospital treatment for gunshot wounds but it was unclear who had fired the shots. One was wounded in the hand, the other in the leg.
Witnesses gave conflicting accounts of whether police used rubber or live bullets.
"They were not targeting the people directly. It was indirect firing," said one Shiite activist who asked to be identified by only his first name, Hussein.
Another resident, contacting The Associated Press by e-mail, said the Saudi authorities also beat some protesters with clubs. The resident said up to 12 protesters were injured, and some were arrested at the local hospital.
It was not possible to verify this information independently.
Videos dated Thursday and posted on social websites showed what appeared to be shooting. Crowds, of mostly men with a few children, were gathered in a small street, separated by an empty plot from the apparent source of fire. Occasional bursts of gunfire can be heard on the videos. The crowd was shouting "Peaceful, peaceful."
Scores of protesters in Qatif marched in the city streets Wednesday night.
Mainly Sunni Saudi Arabia has struggled to stay ahead of the unrest that has led to the ouster of the Egyptian and Tunisian leaders in recent weeks.
Last month, the ultraconservative Saudi government announced an unprecedented economic package worth an estimated $36 billion that will give Saudis interest-free home loans, unemployment assistance and debt forgiveness.
At the same time, it reiterated that demonstrations are forbidden in the kingdom because they contradict Islamic laws and society's values and said security forces were authorized to act against anyone violating the ban.
So far the demonstrations have been small, concentrated in the east among Shiites demanding the release of detainees. But activists have been emboldened by other uprisings have set up Facebook groups calling for protests in the capital, Riyadh, on Friday to demand democratic reforms.
One such group garnered more than 30,000 supporters. The group called the "Honein Revolution March 11" has listed a number of mosques in 17 Saudi cities for protesters to rally.
The group says it strives to have elected officials in Saudi Arabia, including the ruler.
The spread of calls for protests has prompted government officials to issue strong warnings that it will act against activists taking to the streets.
Khalid al-Dakhil, a political science professor from Riyadh, said large scale protests are unlikely to spread outside the east, but he warned that the Arab "revolutionary wave" will catch up with the kingdom.
"Saudi Arabia will be affected by this running wave. But I don't think it will be fatal or dangerous to the political system," he said. However, al-Dakhil said: "A security solution is not a solution. Some changes have to take place," including constitutional and political reform.
Amnesty International called on Saudi authorities to reverse the ban on peaceful protests in the kingdom.
Philip Luther, a spokesman for the international rights group, said authorities should address the need for major human rights reforms and heed the growing calls for change instead of trying to intimidate protesters.
"Reports that the Saudi authorities plan to deploy troops to police upcoming demonstrations are very worrying," he said.
The Interior Ministry has banned demonstrations, saying they contradict Islamic laws and society's values and adding that some people have tried to go around the law to "achieve illegitimate aims."
"Reform cannot be achieved through protests ... The best way to achieve demands is through national dialogue," Saudi Foreign Minister Prince Saudi al-Faisal said Wednesday.
Oil prices had dropped to below $101 a barrel early Thursday, but rebounded a bit to nearly $104 on the New York Mercantile Exchange.
"The news report that protesters were fired upon by police in Saudi Arabia has pulled crude up from the lows," said Phil Flynn, analyst at PFGBest Research in Chicago.