(CNN) -- Police in Bahrain clashed with mourners at a funeral for a 23-year-old man with sickle cell anemia who died in custody, officials said Tuesday.
Mohammed Mushaima, who was serving a seven-year sentence for vandalism, rioting, assaulting a police officer, and resisting arrest, died during the early morning hours, Bahrain's Information Affairs Authority said.
The written statement said a medical examiner determined "the death was natural and caused by sickle cell complications."
But the opposition political party Al-Wefaq accused the government of depriving Mushaima of medical treatment. The government denied that, saying Mushaima had been treated at Salmaniya Medical Complex since being admitted in late August.
In an apparently unrelated development, Bahraini authorities began rounding up nine medics from the hospital Tuesday, a day after an appeals court this week upheld their convictions for their role in anti-government protests last year.
Videos posted on YouTube appeared to show large crowds of marchers at Mushaima's funeral, many holding aloft his picture while his casket was carried through the streets. Another apparently shows protestors after the funeral throwing rocks and Molotov cocktails as police use water cannons to disperse the marchers.
The opposition group February 14 said the protesters "shouted angrily against the King Hamad (Bin Isa Al-Khalifa) and the royal family condemning them" for Mushaima's death.
CNN cannot independently verify the authenticity of these videos.
The Bahrain News Agency said "saboteurs" attacked police who "observed self restraint, ordering the rioters to disperse more than once before intervening to restore order in conformity with the law provisions."
It was the second time in recent days police and protestors have clashed.
On Friday, a 17-year-old protester died in the village of Sadad. The interior ministry said a mob armed with Molotov cocktails and iron rods attacked a police patrol, prompting officers to defend themselves. The attacker was killed, the ministry said.
The Bahrain Center for Human Rights decried the incident as an example of "summary executions." In a statement, the center said that Ali Neamah was taking part in a peaceful protest, and that he was killed by a "deadly shot of a shotgun by the riot police from a close range."
Protests in Bahrain started in February 2011 spurred by uprisings in Tunisia and Egypt. But demonstrations in Bahrain failed to gain the traction of other Arab Spring uprisings after a crackdown by authorities in the island state. The crackdown was backed by troops from nearby Saudi Arabia and the United Arab Emirates.
Last November, Bahrain's Independent Commission of Inquiry issued a report critical of authorities' reactions to the protests.
The independent commission, set up by the king, concluded that the police had used excessive force and torture in their response to the protests in Sunni-ruled, Shiite-majority country.
Abuse of detainees in the crackdown included beatings with metal pipes and batons, and threats of rape and electrocution, according to Mahmoud Cherif Bassiouni, the commission chairman.
The report recommended reforms to the country's law and better training of its security forces, as well as other measures.
Bahrain plays a key strategic role in the Middle East and is home to the U.S. Navy's Fifth Fleet headquarters.