Police from 18 countries have recovered more than 3,500 stolen works of art and ancient artifacts of “great cultural importance” in an operation last year, according to the European police agency.

The haul included a marble Ottoman tombstone, a post-Byzantine icon depicting Saint George and hundreds of coins, Europol said.

Operation Pandora took place in October and November and led to the recovery of 3,561 items and 75 arrests, informs The Guardian.

Officials said they were unable to put a total value on the haul as experts had yet to appraise it.

“Several of the retrieved artifacts are of great cultural importance in the archaeological world,” the Hague-based agency said.

Approximately 500 objects were uncovered in Murcia, south-eastern Spain, including 19 coins that had been stolen from the Archaeological Museum in 2014.

The operation was led by Spanish and Cypriot police who carried out checks on more than 48,500 people, about 50 ships and more than 29,000 vehicles.

Police scoured internet sites, art galleries and checkpoints in their hunt. They also searched scuba-diving schools for items plundered from underwater sites.

In Cyprus, 40 ancient objects were found at the post office in Larnaca, near the island’s main airport.

All airports, post offices and checkpoints to and from northern Turkish-held areas were monitored, and there were “intensified police patrols at sensitive archaeological sites”, Cypriot police said.

“From a total of 44 searches conducted in homes and premises throughout Cyprus, 1,383 artifacts and 13 metal detectors were found and seized.”