Australian Prime Minister Scott Morrison says the country’s major political parties have been hit by a hack on their computer networks. The government says the systems were infiltrated by a “sophisticated state actor”.

Australia’s cyber security agencies believe an unnamed foreign government was behind the attacks earlier this month. Computer networks used by all of the major parties were compromised. The breach was uncovered during an investigation into the hacking of computer servers at Parliament House in the national capital, Canberra.

“Members will be aware that the Australian Cyber Security Center recently identified a malicious intrusion in the Australian parliament house computer network. During the course of this work we also became aware that the networks of some political parties; Liberal, Labor and Nationals have also been affected. But our cyber experts believe that a sophisticated state actor is responsible for this malicious activity,” Morrison said.

Officials say there is no evidence of electoral interference, but Australia is boosting its cyber defenses in response. A federal election is expected in May.

In December, Canberra publicly accused China for the first time of supporting a campaign of cyber espionage to steal commercial secrets.

In 2015 and 2016, there were high-profile attacks on Australia’s official weather and statistics agencies

Beijing has previously denied interfering in Australia’s domestic affairs.

Following the online breach earlier this month there was also press speculation that North Korea or Russia could have been involved. Officials said there was “no evidence” that information had been accessed or stolen.