ISTANBUL, Dec. 21 (Xinhua) -- Turkish police on Thursday seized 26,456 ancient artifacts in the country's most extensive anti-smuggling operation and detained 13 suspected smugglers, a police statement said.

The Istanbul-based operation was launched in five provinces following a three-month-long technical and physical surveillance, the statement said, noting the suspects are believed to be planning to sell the pieces abroad.

Among the confiscated relics are a three-thousand-year-old Mycenaean sword, known as Achilles sword, and coins, plinths and stone art pieces that can be traced back to the Byzantine and Roman Empires as well as the Middle Ages, showed a police video.

"This operation reveals the gravity of the situation in Turkey regarding illegal trafficking of historical artifacts," Nezih Basgelen, an archaeologist and editor of the Archaeology and Art magazine, told Xinhua.

Due to demand from private collectors and museums abroad, the smugglers have long been digging Turkey's archaeological sites and looting its ancient tombs and cairns "with big efforts," he said.

"From the 19th century onward, it is very apparent that many of Turkey's ancient artifacts have been smuggled abroad upon demand of European and American collectors," the archaeologist added, urging the authorities to improve the existing legislation and adopt an appropriate archaeological record system.