Two men were shot dead as protests erupted among the Shiite minority in Saudi Arabia's oil-rich east, the government said on Thursday, in clashes that prompted leaders from both sides to call for calm.
The deaths bring the toll since Sunday to four, with at least nine other people wounded, including two policemen and one woman, said the interior ministry.
Sunday's deaths triggered clashes the following day, when demonstrators took to the streets in the mostly Shiite Qatif region of Eastern Province to protest the suspicious death of 19-year-old Nasser al-Mheishi, whose wounded body had been found near a police checkpoint in the town of Shweika.
On Thursday, the government and Shiite leaders warned against the escalating tensions.
In a statement carried by SPA state news agency, the Saudi interior ministry called on leaders in Qatif to control "those who are misled to avoid innocent casualties."
In response, Shiite clerics and activists warned against the dangers of a "deteriorating situation."
A prominent cleric who spoke to AFP, Munir Khabbaz, warned of "grave" consequences "if the language of bullets takes over."
Human rights activists in Eastern Province also warned of escalating tensions, adding the government response in recent days has been counterproductive.
"The heightened security response does not bring stability at a time when we're calling for the (perpetrators) to be punished and the causes behind the violence to be investigated," said Walid al-Sleisi.
In its statement, the interior ministry said the two men were shot late Wednesday as police exchanged fire with gunmen who "infiltrated" the funeral of another protester.
"These casualties were sustained during exchange of fire with unknown criminals who infiltrated citizens and opened fire from residential areas," it said.
It said "a number of security checkpoints and vehicles have since Monday been increasingly coming under fire in the Qatif region by assailants motivated by foreign orders," in an apparent reference to Shiite Iran which champions the cause of Shiite minorities in Arab countries.
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"Security forces have been exercising self restraint as much as possible," it added.
Medics have confirmed reports by witnesses and activists that two Shiites were shot dead during the funeral.
Ali Abdullah Al Qarayrees, 26, from the town of Awamiya, and Munib al-Sayyed Al-Adnan, 20, from Shweika, were "shot by security forces during demonstrations," one witness told AFP.
According to medics, Ali al-Felfel, 24, died Monday of wounds after police fired at protesters who had taken to the streets in response to the death of the 19-year-old Mheishi.
Protests erupted again Wednesday in Qatif while local dignitaries said the province's governor, Prince Mohammed bin Fahd, promised the interior ministry would probe the death of two Shiites.
Cleric Sheikh Hussein al-Soweileh, who was part of a delegation of Shiite dignitaries from Qatif who met the governor on Tuesday, said the latter "has asked us to bring calm to the street, mainly as (the annual Shiite commemoration period of) Ashura approaches."
The ministry warned Thursday it would not tolerate any more unrest.
The security forces have been ordered to "deter" those who consider breaking the law and have been authorised to "deal with the situation."
"The interior ministry realises that the aim of those trouble-makers is to cause futile confrontations between the people and security forces, as ordered by their masters abroad," it said, once again referring to arch-rival Iran.
In October, 14 people including 11 policemen were wounded during clashes with security forces and demonstrators in the same area.
At the time, the interior ministry in the Sunni-ruled kingdom blamed "outlaws" for the violence and blamed Iran for the clashes.
The overwhelming majority of the estimated two million Saudi Shiites live in Eastern Province, which neighbours Bahrain where authorities, supported by Saudi-led Gulf troops, earlier this year crushed a Shiite-led protest.
Shiites in oil-rich Saudi Arabia often complain of being marginalised.