Japan has asked China to stop taking anal swab tests for Covid-19 on its citizens when they enter the country.
Some have complained that the procedure caused them "psychological distress", officials say.
China, which has largely brought the virus under control, started carrying out anal swabs in January.
Last week, it denied it had required US diplomats to undergo such tests after US media reported some had complained about the procedure.
"Some Japanese reported to our embassy in China that they received anal swab tests, which caused great psychological pain," Chief Cabinet Secretary Katsunobu Kato said.
It was not known how many Japanese citizens received such tests, he added.
The tests are used on some of those quarantined or entering China, he also said, noting their use "has not been confirmed anywhere else in the world".
China had not so far responded to the request, he said, adding that the Japanese government had made the request through the embassy in Beijing.
Some Chinese cities have introduced anal swabs, with local experts claiming they can "increase the detection rate of infected people".
At the time of their launch, state media reported those tests had been "controversial among experts", and that they were far less efficient than tests in the upper respiratory tracts.
The existing tests were preferred, as they believe most people contract the virus orally, they said.
The tests involve inserting a cotton swab 3-5cm (1.2-2.0 inches) into the anus and gently rotating it.