Magritte's personal trademark was the bowler hat
A painting by surrealist Rene Magritte worth 750,000 euros (£675,000) has been stolen in broad daylight from a Belgian museum, curators say.
The 1948 nude entitled Olympia was stolen by two unidentified men, one of whom was armed, police said.
It was stolen from a gallery dedicated to Magritte's life and work at his former home in northern Brussels.
Magritte died in 1967 and is recognised as one of the most influential artists of the 20th Century.
The painting depicts the surrealist's wife, Georgette, lying on her back with a shell on her stomach.
It was part of a permanent exhibition in a house in Jette where the artist worked for nearly 24 years, and is separate from the city's Magritte museum which opened in June.
The theft happened shortly after the museum opened on Thursday, officials said.
"Two people, one Asian-type, one speaking English and one French, broke in, armed with a gun," Andre Garitte, the museum's curator told AFP.
The thieves forced museum staff to lie down on the grass as the robbery took place and then fled, he added.
Two visitors were reportedly in the museum at the time of the robbery. No shots were fired and no injuries were reported.
Entry to the museum is by appointment only.
Magritte's work has inspired pop and conceptual art, the cover of a Rolling Stones record, a video by Oasis, and songs by Paul Simon and John Cale.
He was influenced by popular art - from the slapstick of Laurel and Hardy to the detective novels of Dashiell Hammett - and started as a commercial artist, designing covers for sheet-music, posters and even wallpaper.
But in his paintings, he wanted to make people think about what he called "the mystery without which the world would not exist," by showing familiar objects in shocking or dream-like surroundings.