Australian government and institutions are being targeted by a sophisticated state-based cyber hack, Prime Minister Scott Morrison says.

Mr Morrison said the cyber attacks were widespread, covering "all levels of government" as well as essential service providers and businesses.

He did not identify a specific state actor, adding that no major breaches had been made.

"We know it is a sophisticated state-based cyber actor because of the scale and nature of the targeting and the trade craft used," Mr Morrison said.

Last February, Australia's main political parties and parliament were hit by a "malicious intrusion" on their computer networks carried out by a "sophisticated state actor".