A 20-year old Bahraini died on Friday from injuries suffered during clashes with security forces, the Gulf's main opposition movement said, but the government said there was no evidence police were responsible.
It was the second death reported since the protests on February 14, which marked the second anniversary of an uprising to demand democratic reforms in the US-allied Gulf Arab state.
"Martyr Mahmoud Jaziri had suffered direct firing from close range in the head by regime forces during peaceful protests for the anniversary of the start of the Bahraini revolution," opposition movement Wefaq said on its website.
Samira Rajab, Bahrain's information minister, told Reuters investigations into the matter were ongoing.
"All we know is that he was hit by a sharp object on his head, but there is no evidence that this act was committed by the police," she said.
Jaziri's funeral may take place on Saturday, opposition sources said.
Mass protests erupted in February 2011 at the height of the Arab Spring and were crushed. Small demonstrations demanding greater rights for Bahrain's Shi'ite majority and an end to the absolute power of the Sunni ruling family have continued.
The kingdom saw almost daily demonstrations in the run-up to the anniversary of the revolt, putting Bahrain on the front line of a region-wide tussle for influence between Shi'ite Muslim Iran and Sunni Arab states such as Saudi Arabia.