An 18-year-old Bahraini died Friday, nearly two months after he was shot in the head near a top opposition cleric's home, Amnesty International said.
Mustapha Hamdan, who was shot on January 26 near the home of Sheikh Isa Qassim, died of cardiac arrest, Amnesty's Bahrain researcher Ariel Plotkin told AFP.
Plotkin said Hamdan had been brain dead as a result of the shooting.
Witnesses said Hamdan was shot in the head during a police raid on Qassim's home in a suburb of the capital Manama, where protesters had been staging sit-ins after the cleric's citizenship was revoked last year.
The interior ministry did not respond to a request for comment on the news Friday.
Bahraini rights groups meanwhile blamed state security forces for Hamdan's death.
The London-based Bahrain Institute for Rights and Democracy (BIRD) described the teenager's death as "an extrajudicial killing by the Bahraini government".
A joint statement released by four rights groups, including BIRD and the European Centre for Democracy and Human Rights, said Hamdan was "the victim of excessive use of force" and urged authorities to grant UN investigators access to the country.
Home to the US Fifth Fleet, Bahrain has witnessed continuous unrest since 2011, when a string of protests inspired by the Arab uprisings erupted demanding an elected government.
Authorities in the tiny Gulf kingdom, ruled for more than two centuries by the Sunni Al-Khalifa dynasty, have consistently accused Iran of fomenting unrest in Bahrain.
Bahraini authorities have increasingly tightened their grip on dissent in the majority Shiite country, drawing harsh condemnation from international rights groups.
Parliament this month voted unanimously to grant military courts the right to try civilians charged with any act of "terrorism".
Rights activists fear Qassim, currently detained over a string of charges linked to money laundering and illegal fundraising, could be among the first to face court-martial.