WASHINGTON --- Sen. Edward M. Kennedy, ill with a brain tumor, was hospitalized Tuesday but quickly reported feeling well after suffering a seizure at a post-inauguration luncheon for President Obama.

"After testing, we believe the incident was brought on by simple fatigue," Dr. Edward Aulisi, the chairman of neurosurgery at Washington Hospital Center, said in a statement released by the senator's office. "He will remain ... overnight for observation, and will be released in the morning."

The statement said the 76-year-old senator "is awake, talking with family and friends, and feeling well."

Sen. John Kerry, D-Mass., told reporters he and Mr. Kennedy's wife, Vicki, grabbed the senator as he became ill.

Sen. Chris Dodd, D-Conn., quoted Mr. Kennedy as saying, "I'll be OK, I'll see you later," as he was put into an ambulance.

Mr. Kennedy had appeared in good health and spirits a few hours earlier when he stepped out of the Capitol and onto the inauguration platform.

Sen. Jay Rockefeller, D-W.Va., told reporters that Mr. Obama noticed when Mr. Kennedy became ill and rushed over to his table.

"There was a call for silence throughout the room," he said. "The president went over immediately."

In his remarks, Mr. Obama said his prayers are with the stricken senator, his family and his wife.

Sen. Robert C. Byrd, 91, also left the luncheon early, but his office and others said his health was not the reason.

Mr. Byrd "is currently in his own office ... and is doing fine, though he remains very concerned about his close friend, Ted Kennedy," said Mark Ferrell, a spokesman for the West Virginia Democrat.

Mr. Kennedy was diagnosed in May with a particularly aggressive type of brain tumor, called a malignant glioma, after suffering a seizure at his Massachusetts home. One doctor not connected with his care said it's not unusual for patients recovering from brain tumors to suffer seizures.