PARIS — With impeccable timing and taste, thieves in the wee hours of Tuesday morning plundered an art museum in the Netherlands that was celebrating its 20th birthday and made away with seven borrowed paintings, including valuable works by Picasso, Monet, Gauguin, Matisse and Lucian Freud.

The Kunsthal museum in Rotterdam — which was exhibiting a private collection owned by the Triton Foundation — was closed to the public after the theft, but the bare spaces on its walls were visible to photographers through windows in its modern building by Rotterdam’s museum park and busy Maasboulevard.

The theft was the latest alarm about museum security in Europe, now a prime hunting ground for art thieves. In 2010 five paintings, including a Picasso and a Matisse, together valued at about 100 million euros, or about $130 million, were stolen from the Musée d’Art Moderne in Paris; they are still missing.

Police investigators combed the grounds of the museum and studied surveillance video for clues to the burglary, which they said happened about 3 a.m. and set off an alarm linked to a security agency. But by the time police arrived soon after, the works had vanished.