The raid took place yesterday at dawn, and is the biggest art heist in the Netherlands since 1991 when 20 paintings were stolen (and soon recovered) from the Van Gogh museum in Amsterdam.

Roland Ekkers, from Rotterdam Police, said: “The alarm system in the Kunsthal was supposed to be state-of-the-art. But somehow the people responsible for this found a way in and a way out and they found time to take seven paintings. So that’s something that is part of our investigation right now.”

The exhibition was celebrating the museum’s 20th anniversary.

Entitled “Avant-Gardes” the exhibition consists of 150 works from the Triton Foundation collection.

The stolen paintings include Picasso’s “Head of a Harlequin”, Matisse’s “Reader in White and Yellow”, Freud’s “Woman with Eyes Closed”, and two London landscapes by Monet including “Waterloo Bridge” and “Charing Cross Bridge.”

The art works, potentially worth hundreds of millions of euros if sold legally at auction, have been registered as stolen on The Art Loss Register.