A wide range of political and private-sector organisations in Australia have come under cyber-attack carried out by a “sophisticated state-based cyber-actor”, the Australian government has revealed.

Scott Morrison, the prime minister, disclosed the far-reaching attacks at a media conference in Canberra on Friday, while the defence minister, Linda Reynolds, declared that malicious cyber-activity was “increasing in frequency, scale, in sophistication and in its impact”.

The government did not say which country it believed was responsible, except to say it was “a state-based actor, with very significant capabilities”.

The prime minister declined to respond to a specific question about whether it was China, after months of tensions in its relationship with Australia, but security experts later said they believed it, Russia and North Korea were the only countries that fell within Morrison’s description.

“I’m here today to advise you that, based on advice provided to me by our cyber-experts, Australian organisations are currently being targeted by a sophisticated state-based cyber-actor”, - Morrison told reporters.