DUBAI, United Arab Emirates - Bahraini authorities on Sunday put to death three men found guilty of a deadly bomb attack on police, the kingdom's first executions since an Arab Spring-inspired uprising rocked the country in 2011.

The executions of the Shiite men drew swift criticism from human rights groups and sparked outrage among opponents of the Sunni-ruled government, who see the charges as politically motivated. Activists allege that testimony used against the condemned men was obtained through torture.

Bahrain's public prosecution said the death sentences were carried out by firing squad early in the day. The executions were the first in the U.S.-allied nation since 2010 and followed a spike in protests in solidarity with the convicted men.

Abbas al-Samea, Sami Mushaima and Ali al-Singace were found guilty in 215 of killing two Bahraini policemen and an Emirati officer deployed to bolster the country's security forces in a 2014 bomb attack. Their death sentences were upheld by a Bahraini court last Monday.

Bahrain is a tiny island nation off the coast of Saudi Arabia that hosts the U.S. Navy's 5th Fleet, which patrols the waters around the Arabian Peninsula and is the naval counterweight to nearby Shiite powerhouse Iran.

Government forces crushed the 2011 uprising with help from allies Saudi Arabia and the United Arab Emirates, but the country continues to face low-level unrest led by a majority Shiite population that feels marginalized by the Sunni monarchy.

Hundreds of protesters took to the streets Saturday in solidarity with the condemned men as rumors spread that their executions were imminent. Images shared on social media showed activists blocking roads with burning debris and hurling petrol bombs in clashes with police.

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Nicholas McGeehan, a researcher who monitors Bahrain for Human Rights Watch, called the executions inflammatory and unjust. He urged the kingdom's allies to "publicly and unequivocally condemn these killings."

Protests and clashes continued Sunday despite a heavy presence of riot police deployed in predominantly Shiite areas. Witnesses said shops were shuttered in Daih, where the 2014 bombing happened. Garbage bins were seen overturned and set alight in the streets.

One police officer was injured when several people shot at a police patrol in Bani Jamra, west of the capital Manama, the Interior Ministry said Sunday. It gave no further details.

The Ashtar Brigade, a Shiite militant group that analysts say has claimed some 20 bombings in Bahrain since 2013, took responsibility for the attack on the police officer on social media. The Associated Press could not immediately verify the post, though it came in a forum often used by the group.

"We announce through this statement that all options are open and all targets are monitored," said the group, which prosecutors have linked to the three men executed Sunday.

Al-Samea and Mushaima alleged they were subjected to electric shocks, beatings, cigarette burns, sleep deprivation and sexual assault while in custody, Amnesty International reported in 2015. Al-Singace's mother says her son was also tortured, according to British rights group Reprieve.

"It is nothing short of an outrage — and a disgraceful breach of international law — that Bahrain has gone ahead with these executions," Reprieve director Maya Foa said. "The death sentences handed to Ali, Sami and Abbas were based on 'confessions' extracted through torture, and the trial an utter sham."

Government officials did not respond to a request for comment Sunday on allegations that torture was used against the men. Bahraini officials have previously said the government is opposed to any kind of mistreatment and has safeguards in place to prevent it.

Bahrain's last execution was of a Bangladeshi man in 2010. A number of death sentences have been issued since then.

The three put to death Sunday were the first who had held Bahraini citizenship executed since 1996, according to Reprieve, though they were technically stateless at the time of their deaths after being stripped of their citizenship when convicted.