Experts will now determine whether the recovered painting is authentic, the spokesman said.
About $307,000, denominated in euros, was recovered during the anti-mafia searches, along with several luxury cars.
The raids took place simultaneously in several locations on Friday, from the island of Majorca to Malaga in the south and Valencia to the east.
Twenty people, including Gennadios Petrov, an alleged Russian mafia boss, were arrested in the operation, and bank accounts totalling $18.4m have been frozen.
The Russian mafia group is "one of the four biggest in the world", Spanish police said.
The organisation used Spain as a base for its senior leaders and for laundering money made from illegal activities in Russia and other former Soviet states, the police say.