Romanian authorities have detained 25 people who are suspected of being members of an international gang of cyberthieves who hacked into banks, cloned payment cards and used them to steal over US$15 million.

The group is believed to have over 52 members of Romanian and other nationalities, and broke into computer systems belonging to banks from Puerto Rico, a U.S. territory, and Muscat, Oman, according to the Romanian Directorate for Investigating Organized Crime and Terrorism (DIICOT).

The hackers used the unauthorized access to steal payment card data associated with the accounts of large corporations and then used the data to create fraudulent copies of those cards. The cloned cards were distributed to members of the group who used them to withdraw money from ATMs in different countries, DIICOT said Sunday.

The withdrawals were performed in batches over very short periods of time and typically on non-business days according to Romanian prosecutors. On Feb. 20, 2013, for example, members of the gang withdrew $9 million from ATMs in Japan. On Dec. 2 that same year, the gang made around 4,200 withdrawals from ATMs across 15 Romanian cities, totalling $5 million.

Fraudulent withdrawals were also made in the U.S., Belgium, Canada, Colombia, the Dominican Republic, Egypt, Estonia, Germany, Indonesia, Italy, Latvia, Malaysia, Mexico, Pakistan, Russia, Spain, Sri Lanka, Thailand, Ukraine, the United Arab Emirates and the U.K, DIICOT said.

Romanian authorities executed 42 house search warrants in six cities on Sunday, seizing laptops and mobile phones believed to have been used by the gang’s members. They also seized €150,000 ($163,000) in cash, gold bars weighing 2 kilograms and paintings.

The group’s leaders invested some of the stolen money in real estate and movable goods that will now be placed under restrictions pending the investigation, DIICOT said.

This is not the first cyberheist that involved hacking into financial institutions, cloning cards and performing carefully timed, large-scale ATM withdrawals around the world. In fact, the case might be linked to a larger $45 million cybercrime campaign reported by U.S. authorities in 2013.

In May 2013, the U.S. Attorney’s Office for the Eastern District of New York announced the indictment of eight suspected members of an international cybercrime organization that hacked into the systems of global financial institutions, stole prepaid card data and eliminated withdrawal limits.

U.S. prosecutors described two cyberheists attributed to the gang at the time, one involving cards issued by the National Bank of Ras Al-Khaimah PSC (RAKBANK) in the United Arab Emirates and the other involving cards issued by the Bank of Muscat in Oman. According to the prosecutors, the fraudulent withdrawals were performed in 26 countries, which by and large match the countries listed now by DIICOT.

Security researchers are reporting a trend for cybercriminals to go directly after financial institutions instead of their customers. In February, researchers from Kaspersky Lab reported that a gang called Carbanak stole up to $1 billion from banks and other financial institutions in 25 countries after infecting their systems with malware and carefully learning their internal procedures. The primary attack vector used was spear phishing, targeted emails containing malicious attachments.