The FBI and international partners have at least temporarily dismantled the network of a prolific ransomware gang they infiltrated last year, US officials have announced.

“Simply put, using lawful means we hacked the hackers,” Deputy Attorney General Lisa Monaco said at a news conference.

Officials said the targeted syndicate, known as Hive, operates one of the world’s top five ransomware networks and has heavily targeted hospitals and other health care providers.

The FBI said its work had stopped the group from collecting more than $US130 million ($183 million) in ransomware demands from more than 300 victims.

The FBI quietly gained access to its control panel last July and was able to obtain software keys to decrypt the network of some 1,300 victims globally, said FBI Director Christopher Wray.

News of the takedown first leaked on Thursday  when Hive’s website was replaced with a flashing message that said: “The Federal Bureau of Investigation seized this site as part of coordinated law enforcement action taken against Hive Ransomware.”

Hive’s servers were also seized by the German Federal Criminal Police and the Dutch National High Tech Crime Unit.

It was not immediately clear how the takedown will affect Hive’s long-term operations, however. Officials did not announce any arrests but said they were building a map of Hive’s administrators and affiliates.