A 400-year-old painting that might have been executed by Italian master Caravaggio has been found in an attic in southern France.

Eric Turquin, the French expert who retrieved the painting two years ago, says it is in an exceptional state of conservation and estimates its value at around €$120 million (NZ$197 million).

The picture, whose authenticity has not been established, had been left for more than 150 years in a property in the outskirts of Toulouse.

It was revealed at a press conference in Paris on Tuesday (local time).

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Called "Judith Beheading Holofernes," it depicts the biblical heroine Judith beheading an Assyrian general.

It is thought to have been painted in Rome circa 1604-05.

Turquin told the press conference that there "will never be a consensus" about the name of the artist.

- AAP