Prime Minister Scott Morrison has revealed Australia's political parties suffered cyber attacks alongside the Parliament House computer network several weeks ago by a "sophisticated state actor".

The announcement is likely to intensify speculation that China was behind the attacks, which come just three months before the federal election, though Mr Morrison said there was no evidence of election interference.

Sources are describing the level of sophistication as "unprecedented" but are unable to say yet which foreign government is behind the attack.

The attacks are understood to carry the digital fingerprints of China, though authorities are concerned that another state could be replicating the hallmarks of Chinese intelligence to deflect blame towards them.