Senator Edward Kennedy has been released from hospital, just one day after doctors announced the 76-year-old has a brain tumour.

Kennedy didn't speak with reporters as he left the Boston hospital, but offered a thumbs up and a smile as he walked out with family members.

He will go to his home in Hyannis, Cape Cod for the U.S. Memorial Day long weekend, while awaiting further tests and a treatment plan, according to reports.

The Massachusetts Democratic senator suffered a seizure at home last weekend. He was taken to hospital, where doctors did a biopsy and determined he had a cancerous brain tumour.

The tumour is described as a malignant glioma in Kennedy's left parietal lobe -- a type of tumour that is fatal in roughly half of those diagnosed.

Doctors said Kennedy "has recovered remarkably quickly" from the biopsy.

They did not say whether the tumour was operable.

Kennedy's treatment will be decided after more tests but the common course includes combinations of radiation and chemotherapy.

Experts said Kennedy's condition is serious.

"As a general rule, at 76, without the ability to do a surgical resection, as kind of a ballpark figure you're probably looking at a survival of less than a year," Dr. Keith Black, chairman of neurosurgery at Cedars-Sinai Medical Center in Los Angeles, told AP.

The diagnosis was based on tests conducted on Kennedy following his hospitalization, doctors said.

Meanwhile, Kennedy's friends, supporters and colleagues have been offering kind words and encouragement to the icon of U.S. politics.

U.S. President George Bush described him as "a man of tremendous courage, remarkable strength and powerful spirit."

Allan J. Lichtman, a Democratic strategist and presidential historian, told CTV's Canada AM that Kennedy has been a rock in the U.S. senate, developing respect across party lines.

"Ted Kennedy is of the utmost importance to this country," Lichtman said.

"He is of course the most vivid living link to the early 1960s -- the era we still call Camelot, when the country was still so full of hope, when the civil rights movement was arising, and when we launched the war on poverty."

Lichtman said Kennedy worked with former president Ronald Reagan on renewing the voting rights act, with John McCain on immigration and with President George W. Bush on education.

Lichtman said Kennedy has maintained his Liberal principals for 40 years in the U.S. Senate.

"Whether you agree with those principles or not, to maintain that steadfast a course is extraordinary. He's been able to reach across the line as well -- tributes are pouring in from all sides."

One of the driving forces in Kennedy's life, Lichtman said, has been his desire to help those who have the least.

"This was a man born to great privilege yet he devoted his entire life to helping the downtrodden -- and that is really something in an era where politics is so dominated by wealthy special interest."

Peter Fenn, a consultant to the Democratic Party who worked on Kennedy's first campaign and has family connections dating back decades, said the news of Kennedy's illness came as a shock.

But he said it's too soon to rule out the man who has made a career out of fighting battles.

"This is somebody who almost died in a plane crash in 1964," Fenn told Canada AM. "He's been dealt a lot of adversity, as everyone says he's a human being who has made his share of mistakes, but for almost 50 years he's been fighting in the U.S. senate. He's a lion of the senate if ever there was one."

As recently as last week, Kennedy was an active member of the U.S. Senate, where he has been a leading voice of U.S. liberalism since first being elected in 1962 in a special election.

Earlier this winter, he endorsed the candidacy of Barack Obama, the junior senator from Illinois, to become the Democratic party's presidential nominee.