In the early hours of Monday morning, thieves struck Greece's largest museum, the National Art Gallery in Athens. 

Around 5 a.m. a lone guard spotted a silhouette after an alarm was tripped, and went to investigate, discovering one of the thieves who chose to discard a painting by Dutch artist Piet Mondrian before escaping.

The burglars did successfully purloin another early Mondrian painting from 1905, a representational painting of a windmill very unlike his later abstract linear style.

The other painting taken was Pablo Picasso’s  “Woman’s Head,” from 1939.  The painting depicts a bust of a woman done in a style reminiscent of Picasso’s earlier Cubist works, and was donated to Greece by Picasso in 1949 as an homage to the Greek people for their opposition to Nazi Occupation during World War II. 

A sketch by the Italian 16th-century painter Guglielmo Caccia, who was best known for his altarpieces, was also stolen.  All three artworks were stripped from their frames.

At this point in time it is not known how many people were involved in the thefts.  The thieves appear to have been well organized, the heist taking just around seven minutes to carry out. 

They appear to have spent time on Sunday tripping alarms, so that eventually the National Gallery shut off at least one alarm. The burglars entered through a balcony door and did trigger a motion sensor in the exhibition area.

Museum officials have not been able to give an estimate of what the paintings are worth.

The art gallery from which the works were stolen usually contains mainly 19th and 20th century Greek painting, but a special exhibit showcasing some of the museum's holdings of Western European art had just ended. The gallery was to be closed as of Monday for an extended period of time.

(Report: Christine Bolli)