Montenegrin police have today formally charged Do Kwon, the cryptocurrency entrepreneur behind two digital currencies that lost an estimated $40 billion or more last year, for forging official documents after arresting him on Podgorica airport.

Do Kwon, a South Korean national, and a second suspect had been held yesterday while trying to board a flight to Dubai at Podgorica airport.

Police said in a statement they had found forged Costa Rican passports and a separate set of Belgian passports in their luggage during the encounter.

The two suspects have also been charged before a Podgorica court with forging of official documents, it said.

"Pending completion of the (court) proceedings they will be taken to an investigative judge...for further actions according to an international (arrest) warrant," it said.

It also said that an international warrant had been issued against the two "to ensure their presence before the Southern District Court in Seoul on suspicion of committing several criminal acts in the field of economy."

Several hours after Kwon was detained in Podgorica, the US District Court in Manhattan made public an eight-count indictment against him.

The indictment charges Kwon, who co-founded Terraform Labs and developed the TerraUSD and Luna currencies, with two counts each of securities fraud, wire fraud, commodities fraud and conspiracy.

Both currencies crashed last May, with TerraUSD's price sinking to less than one cent.

The criminal case follows related US Securities and Exchange Commission civil charges against Kwon and Terraform last month.

Kwon had been a fugitive for several months. South Korean authorities issued an arrest warrant for him last September.

South Korean police said today the identity of the suspect arrested in Montenegro had been confirmed as Kwon after his fingerprints matched the information held by the country's National Police Agency (KNPA).