Authorities have warned the highly contagious Omicron adds to the increased risk of COVID-19 transmission as hundreds of millions of people travel around China for the Lunar New Year holiday starting at the end of the month.

Cities such as Luoyang in the central China and Jieyang in the south said on Sunday that travellers needed to report to communities, employers or hotels their trips three days ahead of arrival.

The southwestern city of Yulin said on Saturday those who wanted to enter should fill in a digital form including their health credentials and trip details one day in advance.

At the weekend, the capital Beijing and the southern technology hub each detected one domestically transmitted Omicron case.

So far, at least five provinces and municipalities reported local Omicron infections, while 14 provincial areas found the variant among travellers arriving from overseas.

China is yet to show any solid sign of shifting its guideline of quickly containing any local infections, despite a high vaccination rate of 86.6 per cent.

The strategy has taken on extra urgency in the run-up to the Winter Olympics, to be staged in Beijing and neighbouring Hebei province starting February 4.

Many local governments have already advised residents not to leave town unnecessarily trips during the holiday, while dozens of international and domestic flights have been suspended.

China reported 163 locally transmitted infections with confirmed symptom for Sunday, official data showed on Monday, up from 65 a day earlier.

There were no new deaths on Sunday, leaving the death toll at 4,636. As of January 16, mainland China had 105,087 confirmed cases with symptoms, including both local ones and those arriving from overseas.

The latest increase in infections was mainly driven by more cases in the cities of Tianjin and Anyang, where Omicron has been found in local clusters.

Australian Associated Press