Oscar-winning British actor Maggie Smith, a star of stage and screen for more than seven decades, died in hospital in London on Friday, her sons announced.

"It is with great sadness we have to announce the death of Dame Maggie Smith. She passed away peacefully in hospital early this morning, Friday 27th September," Chris Larkin and Toby Stephens said in a statement.

Smith – a legend of British film and theatre who won a Tony, two Oscars, three Golden Globes and five Baftas – achieved late-career international fame for her portrayal of the kindly Professor McGonagall in the "Harry Potter" film franchise and the Dowager Countess in the hit television period drama series "Downton Abbey."

Born on December 28, 1934, the daughter of an Oxford professor of pathology, Smith made her stage debut in 1952 with the Oxford University Dramatic Society.

She won a Best Actress Oscar for "The Prime of Miss Jean Brodie" in 1969 Oscars and for best supporting actress for her depiction of Desdemona in "Othello" in the same year.

"An intensely private person, she was with friends and family at the end," her sons said.

"She leaves two sons and five loving grandchildren who are devastated by the loss of their extraordinary mother and grandmother," they said, adding their thanks for all the "kind messages and support" they had received. (AFP)