Then British Prime Minister Margaret Thatcher points skyward as she receives standing ovation at Conservative Party Conference in this October 13, 1989 file photo.?More photos

The spokesman Lord Bell said: "It is with great sadness that Mark and Carol Thatcher announced that their mother Baroness Thatcher died peacefully following a stroke this morning."

Baroness Thatcher was Conservative prime minister from 1979 to 1990. She was the first and only woman to hold the post, renowned for the nickname of "Iron Lady" worldwide.

A further statement will be made later, according to the spokesman.

Learning her death, British Prime Minister David Cameron expressed "great sadness," adding that "we have lost a great leader, a great prime minister and a great Briton."

The Queen is "sad to hear the news of the death of Baroness Thatcher and will send a private message of sympathy to the family", Buckingham Palace says.

Over the decade, Thatcher suffered acute short-term memory loss and a series of strokes.

Her husband Denis died in 2003 and her children Mark and Carol both live abroad.