Human rights lawyer Amal Clooney has welcomed the decision by an Egyptian judge to order the release on bail of two Al-Jazeera journalists being retried on terror charges.

The wife of Hollywood actor George Clooney said she was "encouraged" by the ruling in relation to Mohamed Fahmy, who she had acted for, and Baher Mohammed.

The pair were sentenced with their colleague Peter Greste to at least seven years in prison on terrorism-related charges last year in a trial described as a sham by human rights groups.

The three were arrested over their coverage of the violent crackdown on Islamist protests following the military overthrow of president Mohammed Morsi in 2013.

Egyptian authorities accused them of providing a platform for Mr Morsi's Muslim Brotherhood, now declared a terrorist organisation.

The convictions were overturned on January 1 on procedural grounds, but the men were kept in detention pending a retrial.

The decision to grant bail came less than a fortnight after the Egyptian president approved the deportation of Australian Mr Greste.

Mr Fahmy's brother tweeted that he had been let out early today after his £21,500 bail was posted but it was not clear if MR Mohammed had also been released.

Canadian Mr Fahmy, who recently renounced his Egyptian citizenship, is expected to also be deported.

Mrs Clooney said last night: "I am encouraged by the Supreme Court's findings that the trial was unfair, and by today's ruling granting Mr Fahmy bail.

"At the same time, there is no guarantee that a retrial will be carried out in compliance with international standards or result in the full acquittal on all charges that Fahmy deserves. It may also take several months to complete."

She went on: "Mr Fahmy is a Canadian national who was subjected to the same unfair trial process as Mr Greste.

"Mr Fahmy was told by high-level Egyptian officials that, as a dual Egyptian-Canadian national, he must give up his Egyptian citizenship to guarantee a transfer.

"He had no choice but to do so. Then, just days ago, his counsel and the Canadian government were informed that his release was imminent. There is no impediment to his immediate transfer to Canada and (Canadian) prime minister (Stephen) Harper should personally intervene to ensure that the promise that was made by the Egyptian government to his government, and to its citizen, is now honoured."