The parents of an Australian Al-Jazeera journalist detained in the Farm prison in Cairo, Egypt have described the visit to their son as a "horrendous experience".

Juris Greste and his wife Lois went to Egypt to visit their 48-year-old son, Peter, for the first time since he was detained by the Egyptian authorities in December.

Greste and colleague Mohamed Fahmy were sentenced in June to seven years in prison by a Cairo court, which accused them of spreading false news and aiding the Muslim Brotherhood, which has been branded a terrorist organisation by the new government. Producer Baher Mohamed was sentenced to 10 years.

Speaking to the Australian Broadcasting Corporation, Juris Greste described his son as "very sombre," adding: "Had we had a small bucket between us as we were sharing hugs, it might have even overflowed ... with tears and sobs."

Greste, previously in Tora prison, was moved to another prison in Cairo, known as The Farm.

Lois said Greste was being kept in a "dormitory-like situation" with about nine other inmates.

"I think it was probably one of the most difficult days of my life," she added.

"We gave him a hug when we saw him, and also when we left. We thought we had two hours, but it ended up only 45 minutes. It was very emotional to start off with, of course, and then we had to speed through all the important things and before we knew it, time was up."

Juris said he and his wife have prepared for the worst, after discussing the legal options with their son during their visit.

He explained that a member of his family had spent seven years in a Soviet gulag, showing him that "all these things are possible."

Juris appealed to the Australian government " to remember that guys like Peter, at the moment, look like having to pay a very, very high price to be able to learn about what is happening in difficult and challenging places around the world.

"Therefore, my request of them is to keep their interest in Peter's case."

Egypt's President Abdel Fattah al-Sisi has been urged by Australia and the US to release the journalists. Sisi, however said he will not interfere with the country's justice system, which he described as "independent and splendid".

"We must respect judicial rulings and not criticise them even if others do not understand this," Sisi added.