The sentences are likely to deepen divisions between Bahrain's Shia majority, which has been demanding greater political and civil rights, and the Sunni monarchy, backed by Saudi Arabia and the Sunni-dominated Bahraini security forces.
A further 400 people who have been detained are expected to be prosecuted, according to the state news agency.
"The people are very angry," Ali al-Aswad, a Bahraini MP, said. "This comes as a surprise as the defendants were not allowed any lawyers in court and we did not know what was going on." He added that the government had moved quickly to try those it held responsible for the death of the two police officers, but had done nothing to investigate the killing of 26 Bahrainis, including four who died in custody, during the protests.
King Hamad bin Isa al-Khalifa and the Bahraini royal family appear to have adopted a policy of systematically terrorising the Shia of Bahrain, who make up 70 per cent of the indigenous population.
The royals have directed the crackdown against Shia activists and institutions. Shia mosques and shrines are being demolished or wrecked and anti-Shia graffiti has been painted on the walls.
Mohammed Sadiq, of Justice for Bahrain, said: "I have no doubt that they [the defendants] were tortured." He said the authorities were trying to prove that the pro-democracy movement had used violence. "They are trying to provoke people to take up arms but we are going to remain non-violent." In addition to the four men, another three were sentenced to life imprisonment for the same offence.
The script of a Bahraini television documentary, released by the authorities last night, contained the "confessions" of the men, according to a government statement. "Today is the day when justice prevails and when the long arm of the law catches all those who betrayed the nation and undermined its security," the documentary said.
The monarchy appears to have largely succeeded in breaking up the pro-democracy movement since it launched a counter-offensive on 15 March. It has detained doctors who treated injured demonstrators. And patients who had taken part in the protests were dragged from hospital beds, according to the US-based Physicians for Human Rights. Even waving the Bahraini flag has been treated as an offence.
The role of the condemned men in the protest rallies is uncertain. They had denied the charges. "They were activists in their villages and we think they were targeted because of their activities," Nabeel Rajab, head of the Bahrain Centre Human Rights, was reported as saying. "This will deepen the gap between the ruling élite and the population." Other Bahraini sources said the young men, who are all Shia, were not previously known as campaigners or activists.
Bahrain's state news agency said the defendants had "every judicial guarantee according to law and in keeping with human-rights standards." It did not say when the sentences would be carried out.
Relatives who attended the trial said there were discrepancies in the evidence given by the coroner and the prosecution. Three of the four policemen who died were run over by vehicles.
Last night, Bahrain's Information Affairs Authority, said: "The verdict is a clear indication of the community's utter condemnation of barbarous crimes and a profound commitment to the protection of precious lives, human dignity and fundamental rights regardless of [colour], gender, sect and nationality."
The Bahraini government has traditionally claimed that demands for greater rights by the Shia in Bahrain are manipulated by Iran, though US embassy cables released by WikiLeaks say there has been no evidence of this. Iran has denounced the repression in Bahrain, but there has also been an angry response from Iraq, where 60 per cent of the population is Shia and Shia religious parties dominate the government. Grand Ayatollah Ali al-Sistani, the spiritual leader of Iraq's Shia, normally stays out of politics but has criticised the Bahraini government.
Eyewitnesses in Bahrain said masked riot police who raid houses often include officers with Saudi or Jordanian accents or Pakistanis who speak little Arabic. Human-rights activists said Bahrain has long imported police and soldiers.
Spinner falls silent
Bell Pottinger, the British public relations firm, represents the Bahrain government in various capacities: the firm sends out regular emails to journalists, including getting out the Manama administration's line at the start of the opposition protests last month.
However, it was difficult to get the firm to talk about its future in the tiny Gulf state in light of yesterday's death sentences. A call to its office in Manama was referred to the managing director in the country, Matthew Gunther-Bushell, who passed on inquiries to Lord Bell himself. Calls to his office and an email asking about the firm's preparedness to carry on its work were not returned yesterday.
At the start of the protests last month, Bell Pottinger issued several emails to journalists, including one about the administration's readiness to receive the injured in hospitals. The Independent subsequently reported that the regime was detaining doctors.
