"Prime Minister Girija Prasad Koirala has shown evidence of mild acute hepatitis for the past two weeks," his physicians Madhu Ghimire and Shekhar Koirala said in a statement.

"Although the features of the current illness are consistent with acute viral hepatitis E, the exact cause of the illness has not been established beyond doubt," the physicians said.

Ill health has dogged the 85-year-old since he was appointed prime minister after massive pro-democracy protests last April.

He was not present in parliament in May when the new government was sworn in and most government business involving the prime minister takes place at his residence.