Anal coronavirus swabs are now compulsory for anyone arriving in China, despite objections from foreign governments.

The 'humiliating' tests require inserting a cotton swab 3 to 5 centimetres (1.2 to 2.0 inch) into the anus and gently rotating it.

Beijing claims it is a more effective way to detect Covid, but critics say it has left people suffering from 'psychological distress'.

The swab tests were previously used in areas of China that had suffered outbreaks, however they are now being extended to airports, including in Beijing and Shanghai.

Infectious disease doctor Li Tongzeng said virus traces in anal swabs and faecal samples could remain detectable for a longer time than in samples taken from the upper respiratory tract.

Japan's government has slammed China for using the 'humiliating' tests on its citizens

Such swabbing "can increase the detection rate of infected people", the senior doctor from Beijing’s Youan hospital, told CCTV.

Researchers at the Chinese University of Hong Kong (CUHK) said stool tests may be most effective in identifying Covid-19 in kids.

A throat swab on a 52-year-old man in Weinan, a city in northern Shaanxi province, reportedly showed a negative result despite him displaying multiple tell-tale Covid symptoms.

The patient, who had developed a cough and had appetite loss, then tested again using anal and nose swabs which came back positive.

Dr Li added that anal samples are only necessary for key groups such as those under quarantine.

While CCTV said officials are unlikely to condone the use of anus testing on the same scale as other methods because it is "not convenient".