Radical Islamist preacher Abu Hamza's health has deteriorated, the High Court in London heard on Tuesday, as he made a last-ditch legal bid to halt his extradition from Britain to the United States.

The Egyptian-born cleric with a hook for a hand and four other men were set to be sent to the United States after Europe's top rights court gave its green light last week, but they are seeking to block their removal.

To avoid extradition to a US high-security prison, Hamza and fellow terror suspects Khaled Al-Fawwaz, Syed Tahla Ahsan, Adel Abdul Bary and Babar Ahmad must prove there are "new and compelling" reasons not to send them.

Two senior judges hearing the case have been told in papers lodged with the court that Hamza is seeking a temporary injunction pending a request for an MRI scan to be carried out due to his "deteriorating health".

Hamza's lawyer Alun Jones argued that there is "uncontradicted medical opinion that a scan is medically necessary".

Jones adds: "If the applicant (Hamza) is unfit to plead, or arguably so, it will be argued that it would be oppressive to extradite him".

The lawyer said a judge referred to Hamza's "very poor health" at an extradition hearing in 2008.

Hamza, the former imam of the Finsbury Park mosque in north London, is wanted in the United States on charges including setting up an Al-Qaeda-style training camp for militants in the northwestern US state of Oregon.

All five men are already in jail in Britain and none were in court in person to hear the pleas.

A lawyer representing Fawwaz, who was indicted by the US for his alleged involvement in the bombing of two US embassies in east Africa in 1998 which killed hundreds, said he had disassociated himself from Osama bin Laden.

Edward Fitzgerald said Fawwaz had publicly renounced Bin Laden after the Al-Qaeda leader issued a fatwa against Americans in 1996.

The lawyer also pointed to the existence of a diplomatic cable discussing whether Fawwaz should be taken off the US list of terrorist suspects.

He argued that extraditing Fawwaz would breach European human rights laws "by exposing him to the risk of indefinite solitary confinement".

The father of 38-year-old British-born computer expert Babar Ahmad said before he entered the court that he hoped his son would finally get a chance to prove he was innocent of the charges of raising funds for terrorism.

"We have been waiting for eight years and he has been in prison for eight years without trial, without the chance, without being given any chance to prove his innocence," Ashfaq Ahmad said.

"We hope that the courts will look at it and that they will give him a chance to prove his innocence and put a halt on this extradition."