Egypt's former president Hosni Mubarak has been slipping in and out of consciousness, more than a week after he was transferred to a hospital inside a Cairo prison to serve his life sentence, an Egyptian security official said.

Mubarak's wife, former first lady Suzanne Mubarak, and her two daughters-in-law were visiting him in prison this morning after rumours circulated that he had died, the official said.

Mubarak was admitted to the Torah prison after a judge convicted him on June 2 of failing to stop the killings of protesters during last year's uprising which forced him out of power.

The official, who is in the prison, says Mubarak lives only on liquids and yoghurt.