ROME — The Italian police have dismantled an international ring trafficking in what prosecutors say are thousands of ancient artifacts illegally excavated in Sicily.

Maj. Luigi Mancuso, in Palermo for the art squad of the Carabinieri military police force, said Wednesday that investigators were contending that the archaeological digs were commissioned by a London art dealer, William Veres, 64, who had been served with an international arrest warrant.

Twenty Italians were arrested in Italy, one in Spain and one in Germany.

Major Mancuso said Mr. Veres had been arrested in 2017 in Spain in an unrelated investigation by the Carabinieri art experts.

The approximately 20,000 objects recovered included ancient coins, statues and pottery, as well as fake artifacts.