The empty space where Henri Matisse' painting "La Liseuse en Blanc et Jaune" was hanging, right, is seen next to a painting by Maurice Denis, centre, and Pierre Bonnard, left, at Kunsthal museum in Rotterdam, Netherlands, in 2012. File picture: Peter Dejong/AP

Amsterdam - A painting by Pablo Picasso that was stolen from a Dutch art museum in 2012 may have turned up in Romania.

The Romanian organized crime unit DIICOT confirmed on Sunday that it had opened an investigation after the discovery of the picture the day before.

Whether the painting really is the Picasso piece "Tete d'Arlequin" (1971), which was stolen from the Kunsthal Rotterdam, is not yet confirmed and is still under investigation.

The museum is yet to comment on the find. However, a former curator of the collection to which the painting belonged has expressed doubt over its authenticity on Dutch television. Judging from photos, he believes it is only a copy.

The Romanian author Mira Feticu, who lives in the Netherlands and has penned a book on the spectacular art heist, said she found the picture after receiving an anonymous tip-off.

Feticu told the media she had found it buried under a stone in the eastern Romanian region of Tulcea, and had handed it over to the Dutch embassy in Bucharest.

The embassy then contacted the Romanian prosecutors, as a spokesman for the Foreign Ministry in the The Hague confirmed.

The Picasso was one of seven artworks stolen by thieves six years ago. The Romanian perpetrators were arrested in Romania some months later, but there was no trace of the pictures, which also included pieces by Henri Matisse and Claude Monet.

Some of them were burnt, it emerged during the trial in 2014.