Egypt's Nobel Prize-winning writer Naguib Mahfouz is in intensive care at hospital in the capital, Cairo.
Naguib Mahfouz is a much-loved writer in the Middle East
Mahfouz, in his mid-90s, has been in hospital since a fall last month. He is said to be in an "unstable" condition.
His vibrant, colourful portrayal of capital in his Cairo Trilogy won the 1988 Nobel Prize for literature.
He has suffered health problems since being stabbed in the neck in 1994 by an Islamist extremist, angry at his portrayal of God in one of his novels.
After that incident, he was in hospital for seven weeks and suffered nerve damage in his neck, which limited his ability to write and caused his eyesight and hearing to deteriorate.
During his current stay in hospital, he was transferred to the intensive care unit on Monday night after suffering a sudden drop in blood pressure and kidney dysfunction, a hospital official told the Associated Press.
"Despite improvement to some vital signs... his condition remains unstable," the official said, citing the latest medical report.
The writer was taken to hospital in mid-July after he fell during a midnight stroll and sustained a deep head wound.
Naguib Mahfouz's Nobel Prize brought international recognition to a man already regarded in the Middle East as one of its best writers and premier intellectuals.
He has published more than 50 novels, short stories, plays, newspaper columns, essays, travelogues, memoirs and political analyses.