Police in Finland have warned Facebook users about the risk of scams on the social media site's Marketplace platform.
Scams on Facebook's classified ad service have been reported in Finland, Norway, Denmark and Hungary, according to police.
Finland's national cybercrime investigation unit (TVA) took part in a Europol-coordinated investigation about the situation.
The scammers typically create fake Facebook profiles and then target victims selling goods on the platform.
After contacting their targets, scammers use bots to send messages purportedly from a delivery service to them, requesting payment for goods or deliveries.
The victims then follow links to bogus websites, and before it's too late hand over their credit card details, unknowingly giving the scammers access to their money, police explained.
Police in Finland are aware of around 40 victims of such scams in the country. Authorities said nine Ukrainian citizens are suspected of carrying out the crimes in Finland.
The criminal proceeds in Finland totaled more than 60,000 euros, police said.
The international investigation was initiated by Ukrainian law enforcement, according to Finnish police.