Pope John Paul II, suffering from breathing problems and the flu, was rushed to the hospital Tuesday night, Vatican officials said.
The 84-year-old pope has been suffering from the flu since Sunday and apparently suffered a "breathing crisis," a Vatican official told The Associated Press on condition of anonymity.
Earlier, a close member of the pope's staff, American Archbishop James Harvey, said he didn't know the pope had gone to the hospital but knew that the pope had congestion and a slight fever during the day.
The Vatican planned to issue a communique toward midnight Tuesday. In the meantime, cars with Vatican license plates were speeding toward to Rome's Gemelli Polyclinic Hospital where the pope had been taken, according to an AP correspondent at the scene.
It was the same Rome Catholic teaching hospital he was taken to when he was shot in the abdomen in 1981 and at which he has undergone several operations.
As late as 11 p.m. local time, the Vatican appeared calm with no traffic or sign of an alert. The sudden transfer of the pope caught his own staff by surprise.
The frail pontiff has Parkinson's disease, which makes his speech difficult, as well as chronic hip and knee problems.
He was reported to have come down with the flu Sunday, when he made his regular noontime appearance at his window overlooking St. Peter's Square and released a dove in a sign of peace. He appeared remarkably lively, but his words were barely audible.
Until the pope had been taken to the hospital, the Vatican had been issuing reassuring news about his condition, up to Tuesday's late night news cast on Vatican radio.
First word of his transfer to the hospital Tuesday night came from Italian news media.
The Vatican announced earlier Tuesday that it had canceled the pope's engagements for the next few days.
The canceled appointments included John Paul's weekly public audience Wednesday. Besides the traditional morning gathering with the faithful, he had been scheduled to preside at a candle-blessing service in St. Peter's Basilica that evening.
The flu has been sweeping through Italy since December. The Rome region, which is shivering through a cold spell that has dropped temperatures below freezing at night, has been among those hit the hardest.
About 40 percent of the flu cases have been children, with the elderly making up only a small fraction of cases after an aggressive campaign of flu vaccinations for older people, health officials said.
It was not known whether the pontiff had a flu shot.
Vatican Radio asked Navarro-Valls earlier Tuesday if the pope felt the good wishes of people worldwide who are concerned about his health.
"I think so, and as always, the Holy Father is grateful for the prayers of the faithful and of all those who love him. I think this closeness means a lot to him," Navarro-Valls said.
John Paul has kept a busy schedule despite experiencing difficulties with speech and movement that are typical for Parkinson's sufferers.
The last time the pope skipped an audience for illness was in September 2003, when he canceled his traditional Wednesday appointment for pilgrims and tourists because of an intestinal ailment.
The Vatican makes brief announcements when the pope falls ill but rarely provides details about the extent of the illness or any medication he may be taking.