The United States has arrested five individuals at Germany's request in a German-led internationally coordinated investigation of online fraud and money laundering networks that used payment service providers, the U.S. Department of Justice said.

The individuals – four U.S. citizens and one Canadian – were arrested in California and made their first appearance in court Wednesday.

"The United States located and arrested the fugitives in the Central District of California for ultimate extradition to Germany," the DOJ said in a statement Wednesday.

German officials said on Wednesday that 18 people had been arrested earlier this week in searches from Singapore to Canada.

A total of 44 suspects, including six former employees of large German payment service providers, are believed to have taken part in the scheme, which involved stealing the credit card details of some 4.3 million people across 193 countries, German police and prosecutors have said.

"The operators of the network then colluded with German payment service processors – including their executives and compliance officers – to process these payments," the DOJ said in its statement.