US actor George Kennedy, who starred in movies including Cool Hand Luke and the Naked Gun series, has died at the age of 91, his grandson has announced.

Cory Schenkel said his grandfather died on Sunday morning in the city of Boise, Idaho, celebrity news website TMZ reported.

Kennedy won an Oscar in 1968 for Best Supporting Actor in Cool Hand Luke.

As well as the Naked Gun comedies, he also made memorable appearances in Earthquake and Airport 1975.

Mr Schenkel, quoted by TMZ, said the veteran actor had been in poor health since the death of his wife, Joan, more than a year ago, and had been in a hospice for the past month.

Kennedy was born in 1924 in New York where his father worked as a musician and his mother was a dancer.