China has reported its first case of the fast-spreading Omicron coronavirus variant, state media said Monday.

Authorities in the northern city of Tianjin confirmed the case in an individual who entered the country from an undisclosed overseas location, according to the Tianjin Daily newspaper.

The asymptomatic patient tested positive for Covid-19 on Thursday before further tests "confirmed the detection of the... Omicron variant", the report said, adding that the person was being treated in isolation at hospital.

The world's most populous nation is on high alert for potential outbreaks as it prepares to host the Beijing Winter Olympics in February.

Disease control agencies affiliated with the State Council -- China's cabinet -- have ordered stronger virus protocols in port cities like Tianjin, which lies around 140 kilometres (87 miles) from the capital.

Omicron appears to spread faster than the Delta variant, making vaccines less effective but causing less severe symptoms, the World Health Organization said Sunday, while stressing that the data remains patchy. 

China has slowed its number of new virus cases to a trickle through a combination of tight border restrictions, mass testing and targeted lockdowns.

The country recorded 101 new Covid-19 cases on Monday, including 21 imported infections, according to data from the National Health Commission.