A priest was among five people arrested after Spanish police confiscated £52m of jewellery which they said had been taken out of Ukraine illegally.
The 11 gold artefacts were said to date from between the eighth and fourth centuries BC.
Police said the arrests were made in recent weeks after attempts were allegedly made to sell the valuable items in Madrid.
Those arrested included two Ukrainians, one of them an Orthodox Church priest, and three Spaniards.
Officers said the items were part of Ukraine’s national heritage and went missing after being put on display between 2009 and 2013 in an unnamed museum in Kyiv.
The pieces were smuggled out of Ukraine in 2016 and included a belt, earrings and necklaces, Spanish police said.
The artefacts had forged documents to make it look like they belonged to the Ukrainian Orthodox Church, officers added.
An ornate gold belt was seized in 2021 and the rest of the pieces were confiscated in recent weeks.
Police said their investigations were still ongoing.
Read more on Sky News:
At least 15 dead after Bangladesh train crash
Why we’re likely to see more storms like Babet
The pieces are being studied by Spain’s National Archaeological Museum and the country’s Cultural Heritage Institute.
Interior ministry attaches in Albania, Bulgaria, Cyprus, North Macedonia and Ukraine helped with the investigation, police added.