Australia’s government, health and education services and various industries are being targeted by sophisticated state-based cyber attacks, Prime Minister Scott Morrison said Friday.

Morrison said that while the threat wasn’t new, the frequency of the attacks had been increasing over many months and he urged all organizations to improve their cyber resilience.

He didn’t reveal the source of the attacks, but said that there weren’t many “state-based actors” that could engage in such activities. Morrison said the issue was constantly raised with Five Eyes intelligence partners and that he briefed UK Prime Minister Boris Johnson on the matter last night.

“This activity is targeting Australian organizations across a range of sectors, including all levels of government, industry, political organizations, education, health, essential service providers and operators of other critical infrastructure,” Morrison said. “We know it is a sophisticated state-based cyber actor because of the scale and nature of the targeting and the tradecraft used.”

Russia, China and North Korea are among nations that have in the past been accused of sponsoring or carrying out malicious cyber activity, including Russia’s efforts to disrupt U.S. elections. China last year rejected speculation that it was behind an attack on Australia’s Parliament House that breached the systems of the nation’s major political parties.

Australia’s main internet site that provides online access to government services was hit by a cyber attack in March.

During the press conference, Morrison was asked how he would respond to speculation that China could be behind the recent rise in attacks, particularly in light of escalating tensions between the two nations.

“The Australian government is not making any public attribution about these matters,” he said, and also declined to reveal whether the government actually knows the source of the attack.

Morrison said there had been no large-scale personal data breaches as a result of the attacks.