updated 09/14/2012 AT 10:45 AM ET
•originally published 09/14/2012 AT 8:30 AM ET
“We certainly feel a red line’s been crossed,” a palace source tells PEOPLE of the photos, which were taken during William and Kate’s private holiday in France. The source also said that the mood at the palace back home is “one of anger and disbelief.”
News of the photos broke as William and Kate – dressed in headscarf – stepped out to visit Malaysia’s largest mosque, in central Kuala Lumpur.
A statement from a St. James’s Palace spokesman says, “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.”