AFP

Australian journalist Peter Greste is "coping well" in jail since his conviction by an Egyptian court, his parents said on Thursday, but said the family were devastated by the many months he has already spent behind bars.

"In his mind, and in ours too, there's absolutely no way he's going to be there for the next seven years," his mother, 75-year-old Lois Greste, said, while accompanied by her husband, Juris Greste, 78.

Speaking to reporters in Nairobi - where their son was based - on their way home from Cairo, the pair said they remained optimistic that their son would eventually be set free.

Greste and two Al-Jazeera colleagues - Canadian-Egyptian Mohamed Fahmy and Egyptian national Baher Mohamed - were sentenced in June to seven years in jail for defaming Egypt and aiding banned Islamists.

Last week, Greste's family said he would appeal.

"It's a matter of going through the appeals process, and hopefully we will get to the stage where they realise that this is a mistake and free him," she added, noting she was talking about all "three boys."

The visibly distraught couple said their son was now being held in a better facility with a "little more space" compared to the tiny room he and his colleagues had been crammed into a few months ago while awaiting the verdict.

But his father Juris, who proudly held up the Peabody Award for journalism his son had won, said the impact had been terrible for the family.

"Our lives have been completely put on hold for the past eight months... It's difficult to concentrate while Peter is in jail," he said.

"We passionately and absolutely know that a grave and very serious injustice has taken place in Peter's case, and we won't shy away from professing that opinion as long as we can."

The case sparked a global outcry and demands for a presidential pardon amid claims it was a politically motivated trial.

Egypt President Abdel Fattah al-Sisi has said he cannot consider a plea of clemency or a pardon until all legal proceedings have been concluded, and that includes an appeal.

Since the army ousted Islamist president Mohamed Morsi in July 2013, political unrest has reached unprecedented levels in Egypt, with more than 1,400 people killed and at least 15,000 jailed in a government crackdown.