An Egyptian court has ruled that an Al Jazeera journalist jailed without charge since last August will remain in prison for at least another 45 days.

The Cairo criminal court extended Abdullah Elshamy imprisonment on Thursday despite a visible deterioration in his health and a lawyer's request for a release on medical grounds.

The Al Jazeera Arabic journalist has been held without charge since last August, when he was arrested while covering the violent dispersal of a sit-in protest by supporters of the deposed president, Mohamed Morsi.

He has been on a hunger strike for more than four months.

He insists he will not stop until he is released from the Egyptian jails.

On June 4, Elshamy's family visited his cell in a solitary confinement wing of the Scorpion maximum security prison, and were able to see him for just 20 minutes.

Elshamy's health had failed dramatically, they said, adding that government statements that he had visited hospital were false. Rather, he was seen by a medical team in his cell on the instruction of prosecutors.

The family said authorities had covered a small window in his cell, further isolating him.

Elshamy is one of four Al Jazeera journalists held by Egyptian authorities. The others are Baher Mohamed, Peter Greste and Mohamed Fahmy.

They have been charged of false reporting and aiding the Muslim Brotherhood - which the state declared a "terrorist" group in January.

Al Jazeera strongly rejects the charges against all of its journalists and calls for their immediate release.