The paintings were highlights of the museum's collection

Pablo Picasso's Portrait of Suzanne Bloch, and The Coffee Worker by Brazil's Candido Portinari, were taken from the Museum of Art of Sao Paulo.

The theft lasted about three minutes and was caught on security cameras.

A statement from museum officials said the institution had not suffered such a robbery in its 60-year history.

Valuable pieces

The theft, believed to have been carried out by three men, began at 0509 (0709 GMT) and finished at 0512, police said.

The museum's security guards are thought to have been on another floor at the time.

Portinari was an important Brazilian painter

The thieves left behind some of their tools, and police have shut down the museum to search for clues, officials said.

The Portrait of Suzanne Bloch, painted in 1904, is among the most valuable pieces in the museum's collection.

The Coffee Worker (O Lavrador de Cafe) was painted in 1939 and is one of Portinari's most famous works.

O Globo newspaper said that the museum's press service had estimated their joint worth at more than $100m.

However, museum spokesman Eduardo Cosomano told the Associated Press news agency that it was difficult to judge their exact monetary value.

A statement from museum said the two works were on display on the second floor but in different rooms.

Museum officials said they were working with the local and federal police as well as Interpol and the Brazilian foreign ministry and that the building would remain closed while investigations are carried out.