Hezbollah parade
A Hezbollah parade in Beirut. The group was allegedly funding its Syria campaign through international drug trafficking Getty

US and European law-enforcement agencies have arrested the alleged leaders of an international drug-trafficking and money-laundering operation used to fund Hezbollah, the Lebanese Shia group designated a terrorist organisation by the US.

The arrests targeted an external financing wing of Hezbollah that provides "a revenue and weapons stream... responsible for devastating terror attacks around the world," Drugs Enforcement Agency (DEA) acting deputy administrator Jack Riley said in a statement. Working on leads from the DEA in the US, law-enforcement agencies in France, Germany, Italy, Belgium and Colombia have been investigating the criminal operation for more than a year.

Among the four bosses arrested at the end of January was alleged Lebanese money launderer Mohamad Noureddine, who was placed on a US Treasury sanctions list at the end of January for his alleged role in using a front company to fund terrorist groups in Lebanon and Iraq.

"This ongoing investigation spans the globe and involves numerous international law-enforcement agencies in seven countries, and once again highlights the dangerous global nexus between drug trafficking and terrorism," the DEA said.

Under the codename Project Cassandra, law enforcement agencies uncovered a network of money couriers used to collect cash from drug-dealing operations and transport it back to the Middle East. The group was allegedly working with Colombian drugs cartels to traffic millions of dollars-worth of cocaine from South America to Europe and the US.

Taking advantage of the Hawala money-transfer system, which is used widely in the Middle East, Hezbollah's external financing arm was able to launder drug money through Lebanon. Here, it was used to fund the group's activities in Syria, where it is fighting to bolster the regime of President Bashar al-Assad. The group receives funding from Iran, but amid the downturn in oil prices the Islamic Republic had cut the money it provides, forcing the group to increase its revenue from criminal rackets.

"Defending the Assad regime in Syria is a drain on personnel, funds, and military resources," terrorism expert Matt Levitt of the Washington Institute for Near East Policy told CNN.

Hezbollah is designated a terrorist group by several countries including the US, while the EU and the UK proscribe its militant wing but do not regard the group on the whole as a terror organisation.