(CNN) -- Bahrain's government has refuted opposition claims that security officers were responsible for the deaths of anti-government protesters, saying they died of natural causes.
The death of teenager Mohammed Ibrahim Yacoub was one of four reported Thursday by the Bahrain Center for Human Rights.
The opposition group al Wefaq accused Bahraini authorities of running over Yacoub with a police car, an allegation the Ministry of Health denied, according to the Bahrain News Agency (BNA).
An official at the Information Affairs Authority told CNN Friday that the 17-year-old "died from complications of Sickle Cell Anemia following his arrest on Wednesday for rioting in Sitra."
Yacoub, whose age was previously reported as 19, had told police about his medical condition when he started to feel unwell during questioning, Bashmi said.
Police then took him to a medical center but his condition continued to worsen, she said. Intensive care doctors "were unable to revive him, due to internal bleeding and a severe drop in blood pressure," and he died.
An autopsy and investigation have been ordered, she said.
As part of its denial, the Health Ministry released a video purportedly taken at the time of the arrest that it alleges shows Yacoub unharmed. It also released a medical report that indicated Yacoub died from "sickle cell complications" and that his body was "free of injuries."
Bahraini police said Yacoub was arrested Wednesday for participating in "acts of violence and vandalism," BNA reported. Police also said he died of natural causes, the news agency said.
Bashmi also gave accounts of the deaths of two more protesters.
One, named as Saeed Ali Al-Sikri, fell in the bathroom of his home on January 25 and was pronounced dead in hospital, she said. The public prosecutor ordered forensic blood tests but no results have yet been released, she said.
The second, Abbas Al-Shaikh, had been diagnosed with cancer last year, she said. He was admitted to hospital but his condition deteriorated and he died on January 25 after undergoing surgery.
Bashmi said she was not able to give more information regarding the fourth man about whose death questions have been asked, Muntadher Saeed Fakhar.
The reports of deaths come just weeks before demonstrators are expected to mark the one year anniversary of protests demanding political reform and greater freedoms in Sunni-ruled, Shiite-majority Bahrain.
The Bahrain Center for Human Rights said the death toll for January "has now reached 9, making it the highest number in one month since March 2011. The situation in Bahrain is rapidly deteriorating as we reach the one year anniversary of the beginning of the protests."
The State Department issued a travel advisory this week for U.S. citizens, warning of potential unrest in Bahrain.
"Spontaneous and sometimes violent anti-government demonstrations occur in some neighborhoods, particularly at night and on weekends," the warning said.
"The demonstrations have included blockades of major highways, trash can fires and establishment of unofficial checkpoints. Participants have thrown Molotov cocktails and used various other homemade weapons."
Bahraini authorities, according to the statement, have responded with the routine use of tear gas, stun guns and other crowd control measures.
While the State Department said there is no indication that U.S. citizens are being targeted, it said its Embassy personnel and their family members were being relocated to other neighborhoods that have not been involved in the protests.
The protests began February 14, 2011, in Bahrain -- spurred by uprisings in Tunisia and Egypt.
But they failed to gain the traction of other Arab Spring uprisings following a crackdown in February and then again in mid-March by Bahraini authorities -- backed by troops from Saudi Arabia and the United Arab Emirates.
Demonstrators and Bahraini authorities have continued to clash, with the opposition accusing the government of being heavy handed in its crackdown on protests.
In November, Bahrain's Independent Commission of Inquiry issued a report highly critical of the crackdown.
The commission, set up by the king, concluded that police had used excessive force and torture during last year's crackdown on protests. Abuse of detainees included beatings with metal pipes and batons, and threats of rape and electrocution, commission chairman Mahmoud Cherif Bassiouni said at the time.
The mistreatment included physical and psychological torture, intended to extract information or to punish those held by security forces, he said.
The report recommended reforms to the country's law and better training of its security forces.
CNN's Samira Said contributed to this report.