TOKYO, Japan (AFP) — Japan has asked China to avoid using anal swabs to test its citizens for coronavirus, saying the method prompted complaints of "psychological distress".

Tokyo's intervention comes after reports that US diplomatic personnel in China had complained of being subjected to the intrusive tests -- a claim Beijing denied.

China, which has largely brought the virus under control domestically, said last month that anal swabs can be more effective than normal throat and nose tests as the virus can linger longer in the digestive system.

But Japanese government spokesman Katsunobu Kato said late Monday that Tokyo had made a formal request through its embassy in Beijing that people arriving from the country be exempted.

"Our embassy requested Japanese citizens be excluded from anal PCR tests, as some Japanese expatriates... expressed the opinion that the tests produce significant psychological distress," Kato said.

"At this point we have not received a response that they change this... We will continue pressing the issue," he added, noting that there was no information that any other country was using the method.

Asked about the complaint, Chinese foreign ministry spokesman Wang Wenbin said Beijing's testing methods were "science-based" and "in accordance with the changes in the epidemic situation as well as relevant laws and regulations".

Last month, US media said State Department personnel in China had complained about the method, but Beijing rebuffed the reports, saying it had "never requested US diplomatic personnel in China to undergo anal swabs".

Officials in China have used anal swabs to test people it considers at high-risk of contracting COVID-19, including residents of neighbourhoods with confirmed cases as well as some international travellers.

But they have acknowledged it would be hard to use anal swabs as widely as the other methods, which have been used to test millions in mass campaigns, as the technique was "not convenient".