The men were killed by a firing squad Sunday morning in the presence of a judge, physician and a Muslim cleric, State news agency BNA reported, quoting the head of the Terrorist Crimes Prosecution, Ahmed El-Hamady.
The executions came less than a week after Bahrain's highest court upheld their death sentences over a bomb attack in March 2014, the agency said. The executed men belonged to a militant Shia group, the state news agency said. Seven other defendants received life terms.
"Sami Mushaima, Ali Al-Singace and Abbas Al-Samea were convicted of manufacturing and planting improvised explosive devices (IEDs) that were detonated remotely after luring first responders into the fatal ambush," said a statement released Sunday by Bahrain's London Embassy
"Those convicted were members of the listed terrorist group Saraya al-Ashtar, whose members have been convicted of attempting to smuggle weapons and explosives into the kingdom to carry out similar violent attacks."
The two Bahraini police officers and one Emirati officer were killed in the attack during clashes with protesters. The Emirati policeman was part of an Arab Gulf Council force deployed to help Bahraini authorities quell a protest movement.
Demonstrations first broke out in Bahrain
in 2011, during the region's wave of protests called the "Arab Spring." Bahrain's capital, Manama, saw huge -- largely nonsectarian -- street protests five years ago, with weekslong protests taking over the city's then-iconic Pearl Monument, which was subsequently torn down by the government.
Activists took to the streets Sunday to protest the death sentence.
The international rights group Amnesty International said the men were convicted in an "unfair trial."
"This is a dark day for human rights in Bahrain," wrote Samah Hadid, Amnesty International deputy director for campaigns in Beirut. "These executions, the first to be carried out since 2010, are a deeply regressive step for a country whose authorities' have repeatedly trumpeted their commitment to human rights."
Maya Foa, a director of international human rights group Reprieve
, said in a statement posted on its website: "It is nothing short of an outrage -- and a disgraceful breach of international law -- that Bahrain has gone ahead with these executions. The death sentences handed to Ali, Sami and Abbas were based on 'confessions' extracted through torture, and the trial an utter sham."
Reprieve said the executions went ahead despite serious concerns that the convictions were based on evidence obtained under torture.
The three men are the first people executed in Bahrain since 2010, and the first Bahrainis executed since 1996, according to Repreive.
Iran, an overwhelmingly Shiite nation and sharp critic of Bahrain's government, also strongly condemned the execution