Bahrain’s main opposition group, Wefaq, has accused the authorities of responsibility for the death of a detainee in hospital.
The interior ministry said Jaffar Mohammed Jaffar, 23, died on Wednesday at a medical centre where he had been receiving treatment for the past week.
Its statement said he had sickle cell anaemia, but did not explain how this had contributed to his death.
Wefaq said Mr Jaffar had died “due to torture and denial of medical care”.
His family alleged he was subjected to beatings and electric shocks.
But the interior ministry told the Reuters news agency that Mr Jaffar had not been tortured and that he had received full medical care.
Officials also said a government ombudsman had begun an investigation into his death, and that the results would be made public once it was complete, according to the Associated Press.
Mr Jaffar was one of several suspects held in connection with an operation in December that resulted in the seizure of stocks of weapons and explosives, including some being smuggled in by sea.