Human rights lawyer Amal Clooney has slammed the three-year prison sentences handed down by an Egyptian court to three Al Jazeera journalists, including Australia's Peter Greste.

On Saturday, a Cairo judge charged Greste and his Al Jazeera colleagues Mohamed Fahmy and Baher Mohamed of operating without a press licence and broadcasting material harmful to Egypt.

Clooney, who represents Canadian national Fahmy, said outside the court the verdict was not based on evidence.

"Every single third party that has looked at this case from the beginning, from the UN, to the EU, to the US, the UK, everyone has said there is no evidence to sustain any of the charges," she said.

"And Egypt's own supreme court, when they looked at this case, said there wasn't sufficient evidence."

Clooney said the verdict sent out a dangerous message.

"It sends a message that journalists can be locked up for simply doing their job, for telling the truth and reporting the news," she said.

"And it sends a dangerous message that there are judges in Egypt who will allow their courts to become instruments of political repression and propaganda."

Greste, who was deported in early February, said he was "shocked, outraged, angry" at the verdict, which means he is now a convicted terrorist. He said he and his colleagues did nothing wrong.

"We're going to be appealing to the [Egyptian] president. The world's eyes are on Egypt, watching this case, watching whether it has the capacity to follow the rule of law," he said.

Foreign Minister Julie Bishop said in a statement she would pursue all diplomatic avenues with her Egyptian counterpart to clear Greste's name.

Amnesty International said the prison sentences were the "death knell for freedom of expression in Egypt".

The journalists were arrested in Egypt in December 2013, while working for the Al Jazeera network. They were charged with airing false news and aiding the Muslim Brotherhood, a banned organisation in Egypt.

They spent 400 days in jail. In January, 2015, their convictions were overturned, and, in February, Greste was deported to Australia. Shortly afterward, however, a re-trial was ordered.