The United States on Friday offered up to $10 million for information on the prolific Russian-linked Conti hacking group which was blamed for an attack last month in Costa Rica.

The State Department said it would provide rewards of up to $10 million for information that identifies or locates leaders of the hacking group and up to $5 million for information that leads to an arrest or conviction.

According to an FBI estimate, Conti ransomware has had more than 1,000 victims as of January with payouts of more than $150 million.

The payouts make "the Conti ransomware variant the costliest strain of ransomware ever documented," a State Department statement said.

"In offering this reward, the United States demonstrates its commitment to protecting potential ransomware victims around the world from exploitation by cyber criminals," it said.

It pointed to Conti's alleged orchestration of last month's attacks on government institutions in Costa Rica that severely hampered government tax and customs processing.

Little is public about the Conti group's leadership but an unusual leak in February gave some insights.

The leak apparently came due to Conti's professed support for Russia's invasion of Ukraine, with a person releasing internal messages from the group alongside pro-Ukrainian tweets.

Conclusions of analysts who sifted through the documents included that Conti has physical offices in Russia.