A small crowd has rallied at Sydney’s Martin Place in support of three journalists, including Australian Peter Greste, imprisoned in Egypt.

A colleague of imprisoned Australian journalist Peter Greste has urged the public and media not to lose interest in his case.

Speaking to a rally of about 20 people at Martin Place in Sydney, Al-Jazeera’s Andrew Thomas said the case in Egypt was important for free press worldwide.

“Other countries will watch the… success Egypt has had locking up foreign journalists … and they might try to do something similar,” he said.

“That would mean the … dark corners that governments don’t want you to know about wouldn’t be exposed.”

The award-winning Mr Greste, bureau chief Mohammed Fahmy and producer Baher Mohamed were arrested in December.

They’re among 20 journalists accused of airing false news and misleading viewers about the political situation in Egypt.

Broadcaster Al-Jazeera held “a global day of action” for the trio in 30 cities worldwide and on social media on Thursday.

Mr Greste and his colleagues were denied bail at their first appearance in a Cairo court last week.

Amnesty International activism manager Chris Holley told AAP there was hope the men could be released on bail during their next court appearance on March 5.

“Our call is for them to be released unconditionally,” he said.

“But if they’re not released they should be given bail … and I think there’s a prospect that could happen.”

He did admit it was hard to predict how the Egyptian government would act.

Greste’s parents live in Brisbane and could not be at the protest.

In a letter, read by Mr Thomas, they thanked the small crowd and wished “peace and prosperity on the people of Egypt”.