Australia yesterday said a "sophisticated state actor" had hacked the country's main political parties and parliament, just weeks before a closely fought election.
Prime Minister Scott Morrison told lawmakers that investigators looking into a hack of parliament computer systems revealed two weeks ago "also became aware that the networks of some political parties" had been breached.
"Our cyber experts believe that a sophisticated state actor is responsible for this malicious activity," he said.
Australian security agencies said they did not know who was behind the attack or their motives.
It is not yet clear what, if any, material was stolen during the hacks, how long the perpetrators went undetected, or whether it could make some political figures vulnerable to blackmail.
Earlier this month, Australia reported a "security incident on the parliamentary computing network".
That forced users -- including the prime minister and the cabinet -- to change passwords and take other security measures.
Experts warn that attribution is time-consuming and difficult.
"I think it's definitely too early to say," said Fergus Hanson, a cybersecurity expert at the Australian Strategic Policy Institute.
He added, however, that there were only "one or two actors" capable of carrying out such an attack.
Hanson said he would put China "at the top" of the list of possible suspects, but "wouldn't rule out" Russia's involvement.
Chinese foreign ministry spokesman Geng Shuang said such speculation about Beijing was "irresponsible" and an attempt to "smear" the country.