WASHINGTON (Reuters) - The United States joined Australia and Britain in targeting Russia-based Zservers service provider for its role in supporting the Lockbit ransomware attacks, the U.S. Department of Treasury said on Tuesday, citing national security concerns.

U.S. Treasury's Office of Foreign Assets Control also designated two Russian nationals who they said were key administrators for Zservers, a bulletproof hosting services provider or BPH, it added.

"Ransomware actors and other cybercriminals rely on third-party network service providers like Zservers to enable their attacks on U.S. and international critical infrastructure," wrote Bradley Smith, acting Under Secretary of the Treasury for Terrorism and Financial Intelligence.

The action follows joint U.S., UK and Australia cyber sanctions last year targeting the Evil Corp ransomware group, Treasury added.