Le Guignolo (1980)

After the failure of his recent criminal exploits, international con artist Alexandre Dupré sets off for Venice to try to dupe some Japanese business men into buying a fake copy of a stolen Caneletto. On the aeroplane, a stranger asks him to look after his briefcase until after they have landed. Alexandre agrees, but the stranger is shot dead soon after and Alexandre himself becomes the target of enemy agents who are keen to recover the briefcase...

Source: TMDb