J K Rowling's latest honour isn't only for her writing.

The "Harry Potter" author is to receive the PEN/Allen Foundation Literary Service Award, PEN America told The Associated Press today.

Rowling will be presented her award May 16 at the literary and human rights group's annual spring gala in New York. Previous winners include Toni Morrison, Salman Rushdie and Tim Stoppard.

In its announcement today, PEN cited Rowling's advocacy for free expression; her founding of the charitable trust Volant, which supports multiple sclerosis research and other causes; and her nonprofit organisation Lumos, which works to reconnect institutionalised children with their families.

"I'm deeply honoured to receive this award and humbled that my work has been recognised as having moral value by an organization I so admire," Rowling told the AP in a statement. "I've long been a supporter of PEN, which does invaluable work on behalf of imprisoned writers and in defense of freedom of speech."

Rowling's own Potter books have been the targets of censorship and attempted censorship, with the fantasy series' feats of wizardry leading to worldwide allegations that the author advocates witchcraft and the occult.

PEN America president and prize-winning author Andrew Solomon said in a statement that Rowling's writing provides a wealth of "imagination, empathy, humour, and a love of reading, along the way revealing moral choices that help us understand ourselves."

"Through their experiences with Rowling both on and off the page, countless children have learned not only the power of speaking their own minds, but the critical importance of hearing others," Solomon said.

In May, PEN also will honor CEO Michael Pietsch of Hachette Book Group, the US publisher of Rowling's detective novels written under the pseudonym Robert Galbraith. Pietsch has edited Donna Tartt, David Foster Wallace and many other writers and is working with PEN to oppose censorship of books in China.

"As a leader in the fight against pervasive censorship, he has painstakingly reaffirmed literature as more than a consumer good: as a cultural currency in need of vehement protection," PEN Executive Director Suzanne Nossel said in a statement.