The BBC has obtained images of alleged police brutality against peaceful protesters in the Bahraini capital Manama, where fears of a systematic crackdown on pro-democracy activists are growing.
Pictures sent by a human rights activist show police from Bahrain's Interior Ministry, and others in plainclothes, their faces hidden by balaclavas.
The police are seen beating and kicking men who are handcuffed and hooded.
The attack occurred on the outskirts of the capital Manama last Wednesday, 30 March, on a busy stretch of road opposite a popular shopping mall.
Eyewitnesses, some of them crying, described a scene that one said "was like watching a horror film."
But the attack is not isolated.
In recent weeks, the government has cracked down on doctors, bloggers and opposition activists - some of whom have simply "disappeared", according to reports from family, friends and rights groups.
It is difficult to verify the reports, as journalists are not being allowed to report freely from the tiny Gulf kingdom that has been shaken by a wave of pro-democracy protests since mid-February.
At least 27 people have been killed in clashes with security forces, and the protesters' makeshift camp at Pearl Roundabout has been razed to the ground. The Ministry of Interior says that four police officers have also died in the disturbances.
Joe Stork of the US-based Human Rights Watch (HRW) described the apparent police beatings featured in the latest pictures as "extremely disturbing".
"Bahrain is now a state where the police are acting with complete impunity. There is no accountability, not even an effort to cover up what is going on," said Mr Stork, HRW's Middle East and Bahraini expert.
After the BBC sent the pictures to the Bahraini government, the Interior Minister promised "to fully investigate the matter and promptly take legal action against those found guilty, in accordance with the law".
Sheikh Rashid bin Abdullah al-Khalifa went on to state: "The Ministry of Interior has a policy of zero tolerance with regard to any abuse of human rights or misuse of powers."
Bahrain is a country with a majority Shia Muslim population ruled by the Sunni Muslim al-Khalifa family.
Activists say that for years, the government has discriminated against Shia. In this wealthy kingdom, Shia villages are impoverished. Housing is inadequate, schools are often dilapidated, unemployment is rampant. Shia are prevented from working in defence and security police jobs.
As a Sunni lawyer close to the royal family told me "These people (Shia) are not to be trusted. Why would you arm your enemies?"
Many Sunni in Bahrain, fearful of Iran - their Shia neighbour just across the Gulf - believe that what the government calls its law and order campaign is a necessary step.
And the government claims that its actions are designed to prevent the kingdom sliding into what it calls a "sectarian abyss".
But Jasim Husain of the opposition Wefaq Society says the harsh treatment of Shia is having the opposite effect.
"People are being mistreated on the basis of their last name, what they wear, their dialect - that is wrong and dangerous for the country as a whole."
"It is not enough to talk about zero tolerance on police abuse. The government must show zero tolerance," he added.
Activists who describe themselves as "neither Sunni nor Shia but pro-democracy" say the regime is identifying and punishing people along religious lines.
"Shia are being sacked from the education and health ministries, people are being arrested in the hundreds, homes are being raided and ransacked. The number of dead keeps rising. To me this is the beginning of ethnic cleaning," one said.
Nearly 400 protesters - virtually all of them Shia - are said to be in jail,
Activists who had been released by royal decree in the early days of the protest have either been re-arrested or gone into hiding. Six doctors who treated injured protesters are among the imprisoned.
And in a bizarre twist, photos of popular athletes - showing them at Pearl Roundabout supporting the call for democracy in February - were carried on state television.
The athletes were then called live to recant. "They grovel and say they are ready to die for the king," said one journalist who cannot be named. "It is excruciating to watch."
Local journalists who attempt to report the alleged rights abuses say they have received anonymous death threats.
The only Bahraini newspaper which consistently covered the story was accused by state television of spreading falsehoods. Its editor has been replaced.
Foreign journalists have been detained then released after a few hours.
Increasingly, people are terrified to speak to foreign journalists, and with good reason. Many of those who talked openly to foreign reporters just a few weeks ago have been arrested or have gone missing.
Bahrain - once seen in the West as one of the most safe and stable of the Gulf states - has now become an island of fear for many of its Shia citizens.