Senator Kok An and his affiliates were said to have operated “out of casinos and office parks retrofitted for fraudulent activity,” laundered victims’ funds and provided a base to target US citizens, the US Treasury Department added in a statement.

Besides him, 28 people and entities were also targeted by the Treasury.

Kok An runs a business called Crown Resorts, which owns casinos and other buildings in Cambodian cities, the department said.

The US State Department charged in a separate statement that “Kok An and his associates have operated and profited from scam compounds that target US citizens and often use human trafficking victims who are forced to commit unlawful acts under the threat of violence.”

Separately, the US Justice Department announced charges against two people said to have managed a cryptocurrency investment fraud compound in Myanmar and who tried to start another complex in Cambodia.

The state department meanwhile announced rewards for information leading to the seizure or recovery of proceeds linked to “Tai Chang” scam centres in Myanmar said to be conducting online fraud.

Cambodia and Myanmar have emerged as hotspots for cyber scam operations in recent years. Transnational crime groups initially mostly targeted Chinese speakers before widening their reach and stealing tens of billions of dollars annually from victims around the world.

Organised criminal gangs have used casinos, hotels and fortified compounds in Southeast Asian countries as bases to carry out sophisticated online scams, defrauding people through cryptocurrency investment schemes and fake romantic relationships, according to the UN Office on Drugs and Crime.