Two protesters were killed in overnight clashes with police following the arrest of a prominent Shiite cleric, activists said on Monday, raising fears of a new wave of unrest in the Sunni-ruled kingdom's east.
Akhbar Shakuri and Mohammed Filfel, both Shiite, died and a dozen other protesters were wounded during clashes that erupted when police opened fire to disperse a demonstration against the arrest of Sheikh Nimr al-Nimr, said the activists.
The violence occurred in Riyadh Street, the main artery in Qatif city in Eastern Province, they said. The reports could not be independently verified.
The interior ministry described Nimr as an "instigator of sedition" as it announced that he was arrested at Al-Awamiya in Eastern Province on Sunday, after being wounded in the leg while putting up resistance.
He was transferred to hospital and was due to be interrogated, ministry spokesman Mansur Turki said, cited by the official SPA news agency.
"Security forces will not tolerate instigators of sedition who have offended their society and homeland, making of themselves tools in the hands of the nation's enemies," Turki said, apparently referring to the kingdom's main regional rival Iran.
The reported deaths come after Amnesty International said in May that seven people had been killed and a number of others injured in clashes between the authorities and protesters in the Shiite-populated region since November.
Nimr's arrest came 10 days after he had said he was confident that his arrest or killing would be a "motivation" for protests to reignite in the Eastern Province, during a speech at a mosque in Al-Awamiya.
He is considered one of the main proponents of social unrest in the region, where demonstrations first took place in February 2011 after an outbreak of violence between Shiite pilgrims and religious police in the holy city of Medina.
The protests escalated after the kingdom led a force of Gulf troops into neighbouring Bahrain to help crush a month-long Shiite-led uprising against that country's Sunni monarchy.
-- 'Avoid security complications' --
In Manama, the main Shiite movement Al-Wefaq called in a statement on Monday for Nimr's release "to avoid any complication in the security situation" and for dialogue "to overcome the crisis" in eastern Saudi Arabia.
Small groups of Shiites in Qatif last month celebrated the death of Saudi crown prince Nayef bin Abdul Aziz, the country's iron-fisted interior minister, according to videos posted on YouTube.
Nimr was also seen in another video making a fiery speech in which he rejoiced at the death of Nayef, who was interior minister for decades.
The 53-year-old Nimr had called in 2009 for separating the Eastern Province's Shiite-populated Qatif and Al-Ihsaa governorates from Saudi Arabia and uniting them with Shiite-majority Bahrain.
Late on Sunday, Bahrain's Interior Minister Sheikh Rashed bin Abdullah al-Khalifa met his new Saudi counterpart, Prince Ahmed bin Abdul Aziz, in the Red Sea city of Jeddah, Bahrain's state news agency BNA reported.
Prince Ahmed affirmed during their meeting that "security is one in Bahrain and Saudi Arabia" and "insisted on strengthening communication and direct coordination between both brotherly states," BNA said.
Saudi Arabia's estimated two million Shiites, who frequently complain of marginalisation, live mostly in the east, where the vast majority of the OPEC kingpin's huge oil reserves lie.
Activists in the east have called for a fresh wave of protests on social networking website Facebook.