"Head of a Woman," painted in 1939, was among three works taken in the early morning heist on Monday, the authorities said. A fourth work was dropped by the thief, or thieves, during their getaway.

The Picasso portrait, which depicts a woman in a white blouse against a blue background, is inscribed on the reverse: "For the Greek people, a tribute from Picasso." It was donated by the artist in 1946.

Greek police say the raider, or raiders, also made off with Piet Mondrian's "Landscape with a mill," and a pen-and-ink sketch of San Diego de Alcala in ecstasy by Renaissance artist Guglielmo Caccia.

"Landscape with a farm," a second figurative painting by Dutch artist Mondrian -- who is better known for his abstract works -- was left behind as the burglar ran away.

Officers say the intruder, or intruders, interfered with the alarm system several times overnight, setting it off repeatedly so that it was disabled by the museum guards.

At about 4.30am local time (06:30 GMT), the raider(s) broke into the gallery's temporary exhibition area through an aluminum-framed door on a balcony.

During the theft, a motion detector was activated, alerting a guard who chased one thief, but was unable to catch him.

The raid led Citizen's Protection Minister Christos Papoutsis to criticize security at the gallery, which is home to works by Auguste Rodin, Henri Matisse and Peter Paul Rubens.

"I am very sorry because an artwork of huge value was stolen," news agency Agence France-Presse quoted Papoutsis as saying. "This incident should prompt a re-evaluation of the National Gallery's security arrangements."

Athens' National Art Gallery showcases works from the 14th to the 20th centuries, and is best known for its collections of Greek and Renaissance art, including paintings by El Greco, Tiepolo and Brueghel.

The theft took place on the final day of an exhibition entitled "Unknown Treasures," which had featured prints and etchings by Albrecht Duerer and Rembrandt van Rijn.

cnn.com