A spokesman for the royal couple said legal proceedings had commenced in France, the BBC reported.
"St. James Palace confirms that legal proceedings for breach of privacy have been commenced today in France by the duke and duchess of Cambridge against the publishers of Closer magazine France," the spokesman said.
The BBC said William's countenance was a "look of absolute thunder," while Kate appeared "composed and smiling" as the couple left Kuala Lumpur, Malaysia, a stop on their nine-day tour to Sabah in north Borneo.
The couple is angered that Closer published the photos taken last month when the duke and duchess were vacationing in Provence, The Daily Telegraph reported Friday.
The photos are akin to "the worst excesses of the press and paparazzi during the life of Diana, princess of Wales," a statement from St. James Palace said.
Aides to the royal couple said a "red line was crossed."
But Closer's editor, Laurence Pieau, brushed off the criticism, saying the photos "are not in the least shocking," the Telegraph said.
"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," the British newspaper quoted her as telling French television.
"She's a real 21st-century princess. It's a young woman who is topless, the same as you can see on any beach in France or around the world."
The royal family traditionally doesn't take legal action against media, the Telegraph noted.
"Their royal highnesses have been hugely saddened to learn that a French publication and a photographer have invaded their privacy in such a grotesque and totally unjustifiable manner," the palace statement said. "Their royal highnesses had every expectation of privacy in the remote house. It is unthinkable that anyone should take such photographs, let alone publish them."
Officials said the swimming pool where the couple was sunbathing was in plain sight of a public road.
"If two public figures chose to strip off in full view of a public road then they can expect to be pictured," a source at the magazine told the Telegraph, "and they were."
British Prime Minister David Cameron's official spokesman said the government's position is that the royals are "entitled to their privacy," the BBC said.