US Senator Edward Kennedy, a leading Democrat and patriarch of a prominent American political dynasty, has been hospitalised in Boston, a spokesman for a hospital in Cape Cod said on Saturday.
Kennedy, 76, was rushed from the Kennedy compound at Hyannisport, Massachusetts, to Cape Cod Hospital at 9.00am local time, a hospital spokesman told Reuters.
He was then airlifted to a Boston hospital, the spokesman said.
CNN reported Kennedy was taken to Massachusetts General Hospital with symptoms of a stroke, citing a prominent state Democrat it did not identify.
The long-serving Massachusetts senator is a leading liberal voice in the United States and has actively campaigned for Barack Obama in his bid for the Democratic presidential nomination.
Kennedy had preventive surgery at Boston's Massachusetts General Hospital in October to unclog a partially blocked carotid artery in his neck.
The blockage was discovered during a routine check of Kennedy's back and spine, doctors said. A blocked carotid artery can lead to a stroke and death, they said.
Kennedy has suffered from back problems since a plane crash in 1964 in which the pilot and one of Kennedy's aides were killed and the senator was pulled from the wreckage with a back injury, punctured lung, broken ribs and internal bleeding.
The youngest brother of assassinated US President John F Kennedy, Kennedy was elected to the Senate in 1962 and currently serves as chairman of the Senate Committee on Health, Education, Labor and Pensions. He ran for the presidency in 1980.
He helped win an increase in the national minimum wage this year and worked with Republicans to produce broad immigration reform, which failed in the Senate after stiff opposition from conservative Republicans.