The Egyptian president has cancelled an important public appearance on grounds of "severe flu and fever".
Mubarak: Leader since Anwar Sadat was assassinated in 1981
The cancellation came a day after Hosni Mubarak, 75, stopped in the middle of a keynote televised address and walked out for 40 minutes.
State TV said that Mr Mubarak, who is the West's key ally in the Arab world, had "suffered a health crisis".
State media were later reporting that the leader was in "good" health before news of the cancellation emerged.
Mr Mubarak had been due to attend the annual Muslim celebration Lailat al-Qadr on Thursday night.
During the ceremony, the president traditionally awards prizes to people who have shown excellence in reciting the Koran.
However, a parliamentary official announced that Egyptian Prime Minister Atef Ebeid would stand in for the president after doctors advised Mr Mubarak to rest.
"The president is suffering from flu, and following doctors' advice, is resting," a television presenter said before the ceremony began.
Health Minister Awad Taggedine earlier told state TV that Mr Mubarak had "felt his blood pressure drop" on Wednesday and underwent an "electrocardiogram and tests".
Egypt's main newspapers printed pages of pictures of a vibrant Mr Mubarak waving to politicians giving him a standing ovation after he returned to finish the speech on Wednesday.
The daily Al-Gomhouria newspaper ran the headline "The president is fine and he is in good health" in giant red letters across its front page.
The Egyptian Al-Ahram newspaper quoted the president's son, Gamal Mubarak, as saying: "The course of national action will continue and the bounty of the president will continue."
President Mubarak has no designated successor.
He is believed to be grooming his son to follow him as Egyptian leader.