Updated 4.10pm

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 depiction of the Dowager Countess of Grantham Violet Crawley in the hit television 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 work in California Suite in 1978.

She was also nominated for four other Oscars best actress in Travels With My Aunt (1972) and best supporting actress in Othello (1965), A Room With a View (1985) and Gosford Park (2001). 

Her career continued to flourish in her later years, when she became a beloved face to a new generation of viewers through her roles in the Harry Potter series and as Violet Crawley, Dowager Countess of Grantham, in Downton Abbey.

"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.

More to follow.