A 16th-century gold case containing the heart of the only woman to be crowned queen of France twice has been stolen, according to The Telegraph daily.

The British newspaper said in an online report that the 15.24-cm oval reliquary containing the heart of Anne of Brittany was stolen by robbers, who broke in through a window of the Thomas-Dobree Museum in the western French city of Nantes on the weekend.

The queen was buried at Saint Denis near Paris when she died in 1514, but her heart was stored in her family tomb in Nantes to show her loyalty to Brittany.

The reliquary, topped by a gold crown with nine lilies, the royal motif, is considered a masterpiece.

It had been on display at the museum for more than 130 years.

The theft has created outrage among the public.

Philippe Grosvalet, president of the Loire-Atlantique department which owns the museum, said thieves had “attacked our common heritage”, stealing an item “of inestimable value.”