Kate Middleton and Prince William were having breakfast on Friday when they were told some unpleasant news - the paparazzi had struck again and the Duchess of Cambridge was their latest "victim".

A French magazine, Closer, published topless pictures of Ms Middleton sunbathing while they were holidaying in Provence in south-eastern France on the Mediterranean.

Shock, disgust and bewilderment followed as the pictures unleashed a media tornado all over the world.

The royal couple, who left Malaysia Friday night, have launched a lawsuit against Closer for breaching their right to privacy by printing the topless pictures, sources told AFP.

Buckingham Palace earlier reacted with fury, saying it wasa "grotesque" breach of privacy by the magazine that evoked painful memories of press harassment of William's mother Diana.

A royal source told UK daily The Telegraph: "This is disappointing, saddening and turns the clock back 15 years. We have always maintained the position that the Duke and Duchess deserve their privacy, not least when they are on holiday in their own swimming pool."

Closer, a weekly round-up of celebrity gossip, ran a dozen shots of the Duchess under the headline "Oh my God", as she slipped off her bikini top, relaxed on a sun lounger and at one point pulled down the back of her bikini bottoms as William rubbed sun cream on her, Reuters reported.

The magazine said the snaps were taken on the terrace of the Chateau D'Autet, where the couple were said to have spent time last week before leaving for South-east Asia and the Pacific.

It said the chateau is owned by Mr Viscount Linley, the son of the queen's late sister, Princess Margaret, AFP reported.

The spread is a blow to Buckingham Palace as it tries to move on from a scandal over naked shots of Prince Harry that tarred an image bolstered by Ms Middleton and Prince William's wedding, the Queen's 2012 Diamond Jubilee and her Olympic Games appearance.

Closer's editor-in-chief Laurence Pieau described the photos as a "beautiful series" that showed a couple in love and were in no way degrading.

She said the magazine had more intimate shots from the same series that it opted not to publish.

"There's been an over-reaction to these photos. What we see is a young couple, who just got married, who are very much in love, who are splendid," Ms Pieau told French BFM television.

"She's a real 21st-century princess," she said, adding: "It's a young woman who is topless, the same as you can see on any beach in France or around the world."

She said that Prince Harry would feel "less alone" after the pictures were published.

The publication - which set off a stream of mostly angry commentary on Twitter - reopens a debate over the privacy of Britain's royal family and the freedom of the press weeks after a US website published grainy photos of William's younger brother Harry cavorting naked in a Las Vegas hotel room.

"Harry started the fashion: these days the Windsors take their clothes off," Closer said in the photo spread, which it claimed as a world exclusive.

Dubbing the affair "nipplegate" in some cases, a torrent of Twitter commentary on both sides of the English Channel mostly chided Closer for running the shots.

A spoof account for Queen Elizabeth, @Queen-UK,which has nearly a million followers, tweeted "Dear The Sun, Don't even sodding think about it," in a mock threat to the British tabloid newspaper that published the nude photos of Prince Harry.

Privacy lawsuit

Closer, published by Italian company Mondadori, would likely lose any legal case over invasion of privacy, although profits from the issue would likely far exceed any fine faced.

"It's without a doubt an invasion of privacy," said Mr Christopher Mesnooh, a US lawyer who practices in France.

France has one of the world's toughest privacy laws on paper, but the legislation is effectively toothless as the fines for breaching it are miniscule, legal experts and journalists said.

In theory, an editor breaching the law could face a one-year prison sentence and a fine of upto 45,000 euros (S$72,000).

Meanwhile, in a show of unbelievable strength, Ms Middleton managed to smile and laugh her way through a Diamond Jubilee tea party at the British High Commission in Kuala Lumpur.

She sipped tea and chatted to several guests including shoe designer Jimmy Choo. But Prince William at times did appear to have the weight of the world on his shoulders.

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