China on Wednesday sharply criticised Norway for expelling a Chinese academic, in the latest diplomatic fracas to roil relations between the two countries.

Last month the Norwegian government told two researchers at the University of Agder -- one of them Chinese -- to leave the country, the institution's director Tor Aagedal told AFP.

Reports said Oslo took the decision over concerns their work could have military applications.

Beijing has protested to Oslo over the case, foreign ministry spokesman Hong Lei said Wednesday, calling the accusation "baseless".

It "infringed upon the basic rights of the relevant Chinese scholar" and "damaged the academic image of Norway", he told reporters at a regular briefing, urging Oslo to "protect the rights and interests as well as the academic freedom" of the researcher.

China's own universities are run by the ruling Communist Party, which tightly controls discussions of topics it construes as a potential threat to its grip on power and has recently stressed the importance of ideology in higher education.

The dispute is the latest episode in a diplomatic feud that began in 2010, when Beijing halted all high-level contact with Norway after the Nobel Peace Prize was given to Chinese dissident Liu Xiaobo.

The Nobel committee is independent of the government, although its members are chosen by the Norwegian parliament.

Nonetheless whole salmon imports from Norway have since been banned, supposedly on safety grounds and Norwegian citizens have been excluded from a 72-hour transit visa scheme.

Oslo's ambassador -- in post since 2007 -- has reportedly been unable to return home for fear that if he leaves, his successor will not be granted a visa.

Norwegian attempts to normalise political ties with the world's second largest economy have proved fruitless as, according to analysts, China wants to set an example to deter other countries.

- Wind power -

China maintains that it is up to Norway to make a gesture to normalise ties.

Last spring, the Norwegian government announced it would not meet the Dalai Lama during his visit to Oslo, in a controversial decision Prime Minister Erna Solberg described as a "necessary sacrifice" to warm up icy relations.

In September Norwegian media reported that in 2013 then-prime minister Jens Stoltenberg had considered -- but ultimately decided against -- secretly apologising to Beijing for Liu's Nobel award.

The leak appeared to have angered Beijing: soon afterwards, China called off a Norway-China labour conference at the last minute, leaving more than 20 Norwegian businesses in the lurch.

Aagedal told AFP the Chinese academic was on a scholarship to research wind power. The other individual expelled was an applied mathematics professor from "a European country" who worked "in a broad range of fields" but whose research had "no military purpose", he said.

"They left immediately," he said. "We've never been involved in such a case before."

Police had told the university last summer that an investigation was underway, he added.

The Chinese academic's lawyer Nils Anders Gronaas told AFP he was working to have the expulsion order reversed, but he had been denied access to much of the documentation in the case on national security grounds.

His client had caught Norwegian authorities' attention partly because of his links to a Chinese university which has connections with military scientists, he said.

The other individual was "a German national of Iranian origin", he added.

Norway's intelligence services declined to comment.