"From January 27, no vehicles, ships or personnel will be allowed to enter the city, except those with emergency and special missions," Efe news quoted the state-run newspaper as saying in a tweet.
Shantou in Guangdong province has a population of over five million.
It is the first city outside Hubei province, the worst-hit by the disease that originated in its capital Wuhan, to be locked down until further notice.
Media reports said the city's bus services, taxis, ferries and streetcars would be suspended from 2 p.m. on Sunday.
From Monday, private vehicles would also be barred from entering the city, while all passengers arriving would be screened for their temperature, as fever is one of the main symptoms of the disease.
The city of Guangzhou has also decided to shut swimming pools, hot spring bath houses and gyms, and suspended exhibitions and "all large-scale economic and trade activities" to prevent the spread of the virus.
The news comes the same day the Disneyland theme parks in Hong Kong and Shanghai have announced temporary shutdowns, while Beijing suspended inter-state bus services and enforced strict sterilization measures.
China's National Health Commission reported on Sunday that the coronavirus death toll had mounted to 56, while at least 1,975 people been infected, with 324 patients in serious conditions.
The WHO has decided not to declare an international health emergency due to strict measures carried out in China that include complete suspension of transport in and around a dozen cities in Hubei province and cancelling Chinese New Year celebrations.
The symptoms of the new coronavirus, provisionally designated by the World Health Organization as 2019-nCoV, are similar to those of cold but may be accompanied by fever and fatigue, dry cough and dyspnea (shortness of breath).
( With inputs from IANS )