Bahraini authorities on Sunday executed three Shia Muslim men convicted of killing an Emirati police officer and two Bahraini policemen in a 2014 bomb attack, in a move likely to stoke protests in the restive Gulf island kingdom.

The executions came less than a week after the country's highest court confirmed the punishment against Abbas al-Samea, Sami Mushaima and Ali al-Singace, the first death sentences to be carried out since 2008.

State news agency BNA said the men were executed by firing squad in the presence of a judge, doctor and a Muslim cleric.

"Arab Spring" demonstrations led by Bahrain's Shia majority were crushed by the Sunni-ruled government with help from its Gulf Arab neighbours, deepening sectarian rivalry in the war-damaged region.

Authorities last year escalated a crackdown on its Shia critics by imprisoning a top rights campaigner, shuttering the main opposition block and revoking the community's spiritual leader of his citizenship.

Activists condemned the executions and warned the move would undermine security.