By Joseph Menn

SAN FRANCISCO (Reuters) - One of the most prolific Russian-speaking ransomware gangs has claimed credit for a weekend attack on an Australian electric utility serving millions of people.

Australian media reported on Monday that Chinese government hackers were behind the breach at CS Energy, which is owned by the Queensland state in northeast Australia.

Those reports, which came amid high tensions between Australia and China, prompted the utility to issue a statement on Tuesday.

There is "currently no indication that the cyber incident was a state-based attack," the statement cited CS Energy CEO Andrew Bills as declaring.

The ransomware group known as Conti, meanwhile, named CS Energy on its web site for shaming victims and sometimes leaking their data.

"Conti listed CS Energy on its leak site which, obviously, would indicate that one of its affiliates was responsible for the attack," said Brett Callow, a threat analyst at security firm Emsisoft.

The Australian, the Daily Mail and other media directly blamed the attacks on China.

But Callow said that "Conti is believed to be a Russia-based cybercrime operation, not a China-based APT, so it would appear that the attack on CS Energy is simply an addition to the ever-expanding list of financially motivated ransomware attacks." APT is security industry shorthand for Advanced Persistent Threat groups, which are often backed by governments.

Like some other ransomware groups, Conti splits proceeds with affiliates who break into targets before installing its program for encrypting computer files and referring victims to Conti for negotiating payments in cryptocurrency.

Conti and other gangs have increased their attacks on utilities, hospitals and other critical infrastructure in the past year. Western officials and researchers have said some of those groups have ties to Russian intelligence agencies, but no such accusation has been leveled against the Chinese.

(Reporting by Joseph Menn; Editing by Stephen Coates)