China’s foreign ministry said on Thursday it was totally within its rights as a sovereign power to ban two Australian scholars.

China firmly opposes actions that harm the country’s security and spread misinformation under the pretext of scholarly work, foreign ministry spokesman Wang Wenbin told a press briefing.

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The Global Times newspaper said earlier on Thursday, citing unnamed sources, that China had barred entry to two “anti-China” Australian scholars.

The paper, published by the ruling Chinese Communist Party’s official People’s Daily, said the decision to bar Clive Hamilton and Alex Joske came after Australia revoked the visas of two Chinese scholars over “alleged infiltration” in early September.

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Ties have become strained over issues from trade disputes to Australia’s call for an international inquiry into the origins of the coronavirus that first emerged in China late last year, and by accusations of Chinese meddling in domestic affairs.

“This ban is quite unexpected, although I have been on Beijing’s enemy list for some years,” Hamilton said in an email to Reuters.

He added that the ban against him and Joske was “retaliation” for the Australian government’s actions against Chinese scholars and that he had already decided “two or three years ago” it would be too dangerous to travel to China.

“Only when Beijing decides to stop interfering in Australian politics and attempting to bully the Australian government will relations improve. I hope that happens soon,” he said.

In a 2018 book, Hamilton, a professor of public ethics at Australia’s Charles Sturt University, accused China’s Communist Party of a campaign to exert influence in Australia’s domestic politics.

Joske is an analyst at the Australian Strategic Policy Institute, which the Global Times called “infamous for churning out anti-China propaganda and fabricating anti-China issues.”

He said on Twitter that the ban is the “latest in a series of attempts by the Chinese Communist Party to punish those who shine a light on its activities” and that he had also judged the risk of travelling to China to be “too high.”