A previously unknown portrait by Pablo Picasso of French artist Dora Maar -- the painter's best-known muse -- sold for 32 million euros ($37 million) in Paris on Friday, auction house Drouot told AFP.

Entitled "Bust of a Woman With a Flowery Hat", the oil portrait of photographer, painter and poet Maar is a riot of colours and thick, black lines.

It was "sold to a foreign buyer present in the room", the auction house said.

The Spanish master painted it on July 11, 1943 and it was acquired in August 1944 by a private French collector, grandfather of the former anonymous owners.

The sale far outstripped the reserve price of eight million euros ($9.5 million).

Picasso sales are used as a leading indicator for the art market as a whole, which has slumped in recent years.