Police sources in Karachi, where Mr Zardari is in jail, earlier said he had tried to kill himself, a punishable offence under Pakistani law.

Owen Bennett-Jones with the latest from Islamabad

A source close to Benazir Bhutto told the BBC that her husband's alleged suicide attempt in on Tuesday was in fact an attempted murder by the Pakistani authorities.

The BBC's correspondent in Dubai, Frank Gardner, says the source said that Mr Zardari was tortured in custody on Monday night and that Ms Bhutto feared for his life.

Ms Bhutto is currently in Dubai - she faces arrest and jail if she returns to Pakistan after her conviction on charges of corruption.

Denied food and drink

Zardari's lawyer Azizullah Sheikh: "I am the only person allowed to see him."

Mr Zardari's lawyer, Azizullah Sheikh says his client has been denied food, water and sleep for three days and is now in a weakened state with severe neck injuries.

Murtaza Bhutto

Mr Zardari is currently in prison facing charges of corruption and the murder of Benazir Bhutto's brother, Murtaza Bhutto, in 1996.

There is still no official account of what happened, but a police spokesman told reporters on Tuesday that Mr Zardari had used broken glass to cut himself on his neck and wrist and then refused to go to hospital.

They said he was in a detention centre at the time of the incident because police had been questioning him about his alleged role in another murder, that of the lawyer Nizam Ahmed, who was killed in Karachi in 1996.

Owen Bennett-Jones: "There are bound to be counterclaims that he was beaten up in police custody."

BBC Islamabad Correspondent Owen Bennett-Jones says suggestions that Mr Zardari attempted suicide in police custody were bound to lead to counter claims that he was beaten up by the police in the course of their inquiries.

Reports in the Pakistani press said that Mr Zardari, who is still a member of Pakistan's senate, had started a hunger strike to protest at his transfer to the detention centre.

Kickbacks

Mr Zardari has been in prison for over two years. He has been convicted, along with his wife, on one corruption charge, but is currently making an appeal to the Supreme Court in that case.

In April, the Bhuttos were sentenced to five years in prison on charges of corruption. They were accused of having received money from a Swiss-based organisation in what was seen as a money-laundering operation.

Mr Zardari was a major influence during his wife's two terms as prime minister, on both occasions she was suddenly removed from office by the president.