Kazemi was admitted to hospital last June 27, after four days of being interrogated in Tehran's notorious Evin prison for taking pictures of a protest outside its gates.

A witness who saw the 54-year-old photojournalist from Montreal said she was conscious and responding to questions by blinking her eyes.

The witness, whose identity the BBC did not reveal, said Kazemi was brought in by prison guards, who stayed with her in hospital. Doctors were prevented from giving her urgent medical treatment, the witness added.

"The doctors did order a brain scan several times but it wasn't carried out until 12 hours later when she was already in a coma. In a situation like that, every second is vital," the witness told the BBC.

"The scan showed that there were repeated blows of varying intensity. It showed that her head had been hit very hard, causing severe brain damage and bleeding," the source added.

Another source who saw the result of the brain scan raised the possibility that the fatal blow had been struck several days before Kazemi collapsed, according to an hour-long documentary presented last night on the BBC's This World program.

Kazemi's death, and Iran's attempts at covering up the circumstances that led to it, sparked a row with the Canadian government last summer. Canada recalled its ambassador for consultation after Tehran refused the Kazemi family's request to have her body transported to Canada.

Iranian authorities instead buried it in Shiraz, the town of Kazemi's birth, thereby assuring that an independent autopsy could not be performed.

Kazemi's mother, Ezet, had initially given a written request to the Canadian embassy to have her daughter's body transported to Montreal, where Kazemi's son, Stephan, lives.

But she told the BBC she was then threatened into giving Iranian authorities permission to bury the body in Iran. "They said if you don't give permission to bury the body in Iran we will harm you and we will harm Stephan as well," she said.

Kazemi was arrested June 23, but her family and friends didn't receive news of her detention until eight days later. Ezet immediately went to Evin prison, and discovered that her daughter had been transferred to hospital.

At the hospital, her daughter lay in a coma. "I asked the nurse to pull away the bed sheet. They had beaten her up so badly her body was black and blue all over," Ezet said.

Ezet visited her daughter every day. On July 11, Ezet was told Kazemi had died. The day before, someone had turned off Kazemi's life-support machine. Neither her family nor the Canadian embassy had been consulted or informed.

"My child was healthy when they took her to Evin and they gave me back her lifeless body," Ezet said.

The first official pronouncement came from an Iranian official who said Kazemi had died of a stroke. The same official later said he had been pressured to say so by Saeed Mortazavi, Tehran's hardline general prosecutor, who was present at Kazemi's interrogation.

Days later, Iran's vice-president, Mohammad Ali Abtahi, announced that Kazemi had died from a brain haemorrhage caused by a blow to the head.

Kazemi's death quickly fuelled the power struggle between reformist politicians who control the parliament and hardline religious leaders who control the judiciary and back Iran's supreme leader, Ayatollah Khamanei.