A lone thief broke into a Paris museum last night and stole five paintings possibly worth hundreds of millions of euros, including masterpieces by Pablo Picasso and Henri Matisse, French police said today.

A police spokesman said works by Picasso, Matisse, Georges Braque, Amedeo Modigliani and Fernand Léger were reported missing early this morning from the Paris Museum of Modern Art. The total value of the paintings was initially put at €500m (£430m) by the Paris prosecutor's office, but Christophe Girard, the deputy culture secretary at Paris City Hall later said it was "just under €100m".

The pictures are: Le Pigeon aux Petits Pois (Pigeon with Peas) an ochre and brown Cubist oil painting by Picasso; La Pastorale (Pastoral), an oil painting of nudes on a hillside by Matisse; L'Olivier Près de l'Estaque (Olive Tree near Estaque) by Braque; La Femme a l'Eventail (Woman with a Fan) by Modigliani; and Nature Morte aux Chandeliers (Still Life with Chandeliers) by Léger.

The burglary was discovered just before 7am. A single masked intruder was caught on a CCTV camera taking the paintings away, according to the prosecutor's office. A window had been broken and the padlock of a grille giving access to the museum was smashed. The paintings appeared to have been carefully removed from their frames, rather than sliced out.

Police and investigators have sealed off the museum.

Today, visitors climbing the steps to the ornate bronze doors of the museum were informed by written notices that for "technical reasons" they would have to come back another time, while the world's media swarmed around the five police officers on guard outside. By early afternoon, the entrance had been cordoned off and security barriers erected.

Graphic: map - museum of modern art in Paris Photograph: Graphic

Girard, who is deputy to the mayor of Paris, Bertrand Delanoë, said the theft was a "serious crime [against artistic] heritage" that had revealed failings in the museum's security system.

"There are three [security] people in the museum at all times but those three people saw nothing," he said, adding that all five paintings belonged to the museum's permanent collection and were in good condition. Those responsible for the theft, he went on, had clearly been very organised.

Delanoë said: "I want everything to be done to recover these masterpieces."

Patricia Schneider, a New Yorker on holiday in Paris who had come to see the collection, said she was shocked by the news of the theft.

"It feels intrusive when any great artwork is stolen," she said. Her mother, Mimi, added: "That it can happen in this day and age, with all the security measures that are taken, is appalling."

Le Monde reported that the paintings were so well-known that it would be difficult to sell them on the open market. Previous thefts have involved paintings being stolen to order on behalf of private collectors.

The theft is being investigated by the Brigade de Répression du Banditisme, France's elite police armed robbery unit.

Last December, thieves stole a pastel by Edgar Degas worth €800,000 from an exhibition in Marseille. The work, Les Choristes (The Chorus), was found to be missing from the Musée Cantini by a security guard when he opened up. The work, on loan from the Musée d'Orsay in Paris for the exhibition, had been stolen overnight.