For more than a year, the parents of jailed Al-Jazeera English journalist Peter Greste kept up a relentless campaign to free their Australian son from an Egyptian prison.

On Monday, the misery that had been etched on their faces during so many news conferences had been transformed into beaming grins as they bounded over to the microphones once more — this time, to proclaim their son a free man.

"There is still a sense of unreality about it all, much like the day 403 days back when we received a call one night that Peter's in an Egyptian prison," said Greste's father Juris, who donned a festive red shirt and matching hat — a stark departure from his typically subdued attire. "To me, it is yet to quite sink in where we are, what's happened."

What happened was a surprise to many. Greste was released from prison and deported Sunday after a presidential "approval," according to an Egyptian prison official and the nation's official news agency. The official and an Interior Ministry statement said he was released under a new deportation law passed last year.

But the joy over Greste's release was tempered by the news that two of his Al Jazeera colleagues, Egyptian-Canadian Mohammed Fahmy and Egyptian Baher Mohammed, remained jailed.

"He's not going to forget his two other colleagues, there's no doubt that his excitement is tempered and restrained and will be until those guys are free. He won't give up until Baher and Mohamed Fahmy are out of there," said Andrew Greste, his brother.

All three were arrested in 2013 over their coverage of the violent crackdown on Islamist protests following the military overthrow of former president Mohammed Morsi. Egyptian authorities accused them of providing a platform for Morsi's Muslim Brotherhood, now declared a terrorist organization, but officials never provided any concrete evidence.

The three were sentenced to seven to 10 years on charges including spreading lies to help a terrorist organization — a reference to the outlawed Muslim Brotherhood. One month ago, however, a court ordered their retrial.

A security official said Fahmy was expected to be released from Cairo's Tora prison within days; his fiancée said she hoped he would be free soon and deported to Canada. "His deportation is in its final stages. We are hopeful," Marwa Omara told Reuters.

Lorne Waldman, one of Fahmy's lawyers, said he had been in touch with his client.

"Mr. Fahmy is very pleased that Peter was released and hopes that he will be released soon as well."

Elsewhere, Foreign Affairs Minister John Baird spoke with his Egyptian counterpart, Sameh Shoukry, on Sunday, Baird's office said in a statement.

Baird "welcomed today's positive development, and noted that he remained hopeful that Mr. Fahmy's case will be resolved in short order."

'The Marriott Cell'

Many Egyptians see Qatar-based Al-Jazeera as a force set on destabilizing the country, a view that has been encouraged in the local media which labelled the journalists "The Marriott Cell", because they worked from a hotel of the U.S.-based chain.

Al Jazeera journalist Peter Greste was freed from an Egyptian prison on Sunday. (Reuters)

Egyptian authorities accuse Al-Jazeera of being a mouthpiece of the Muslim Brotherhood, the Qatar-backed movement which President Abdel-Fattah el-Sissi toppled in 2013 when he was Egypt's army chief.

The timing of Greste's release came as a surprise, just days after Egypt suffered one of the bloodiest militant attacks in years. More than 30 members of the security forces were killed on Thursday night in Sinai, and ensuing comments from Sissi suggested he was in no mood for compromise.

The Interior Ministry said on its Facebook page that Sissi released Greste under a decree issued in November authorizing the president to approve the deportation of foreign prisoners.

Flight to Cyprus

Australia's foreign Minister Julie Bishop said Greste flew to Cyprus from Cairo. "He was immensely relieved and he was desperate to come home to Australia and reunite with his family," Bishop said.

She said several governments had raised Greste's case with Egyptian authorities. "Prime Minister [Tony] Abbott spoke to President el-Sissi and we had many other governments, including in the region, make representations on Mr. Greste's behalf."

The journalists say they were doing their jobs when detained. Their imprisonment reinforced the view of human rights groups that the government was rolling back freedoms gained after the 2011 uprising that toppled autocrat Hosni Mubarak.

Since the army's overthrow of president Mohammed​ Morsi of the Brotherhood after mass protests against him, security forces killed hundreds of Islamists, imprisoned thousands of others and then rounded up liberal activists charged with protesting without police permission.

Al-Jazeera said its campaign to free its journalists from Egypt would not end until all three were released.

The case has contributed to tensions between Egypt and Qatar, though speculation had been rising that Saudi mediation had improved ties, raising the possibility that Sissi would deport or pardon the journalists.

They were detained in December 2013 and charged with helping "a terrorist group" by broadcasting lies that harmed national security.

Baher Mohamed was given an extra three years for possessing a single bullet. If the authorities decide to free him, resolving his case could be more complex because he does not possess a foreign passport.

"This is what we expected would happen," his brother Assem said. "Those who rule the country, this is not the first time they've done this, there have been foreigners who they have let leave the country when they were in trouble and their Egyptian colleagues are the ones who paid the price."