To some she was "a political pilgrim", to others a "liberal lioness", but there was never debate about Susan Sontag's first love: the written word.

Born in New York in January 1933, she spent her formative years in Arizona and Los Angeles poring over Shakespeare, Hopkins, Hugo, Poe and Mann. However, it was only after reading Jack London's Martin Eden that she decided to become a writer.

"I got through my childhood," she told the Paris Review, "in a delirium of literary exaltations."

At 16 she began studying at the University of Chicago, where she met and married Philip Rieff, a 28-year-old social theory lecturer. They had a son, David, when she was 19 but divorced in 1959

Her studies took her on to Harvard and then Oxford, laying the foundations of what she later termed "probably the best university education on the planet".

Sontag wrote novels, non-fiction books, plays and film-scripts as well as essays.

From 1987 to 1989 she was president of the Pen American Centre, the writers' organisation, where she led a number of campaigns on behalf of persecuted writers.

Salman Rushdie, the current Pen president, expressed his gratitude for her backing over the fatwa issued against him in 1989 for his book The Satanic Verses. "Her resolute support, at a time when some wavered helped to turn the tide against what she called 'an act of terrorism against the life of the mind'."

She caused outrage after the 9/11 attacks by writing in the New Yorker: "Where is the acknowledgment that this was not a 'cowardly' attack on 'civilisation' or 'liberty' or 'humanity or 'the free world' but an attack on the world's self-proclaimed superpower, undertaken as a consequence of specific American alliances and actions?"