More than 18,000 passengers have been blocked from boarding planes, trains and buses to leave Guangzhou, Guangdong province, as of Tuesday after failing to present a negative coronavirus test result obtained within 48 hours, along with a green health code, a senior transportation official from the city said.

Guangzhou which has population of about 18.7 million people, imposed a requirement on Monday that all the city’s air, train and coach passengers must show timely test results to leave the city.

On Friday, the city suspended all bus services between Guangzhou and cities and regions outside Guangdong.

"The move aims to further reduce the flow of people, lower the risk of infection and prevent and control the further spread of the novel coronavirus," said Shen Ying, deputy director of the Guangzhou municipal transportation bureau.

The number of passengers leaving Guangzhou has been sharply reduced since the end of May. Shen said that about 61,000 passengers left Guangzhou by plane, train and bus on Tuesday, a reduction of 75 percent from the figure recorded on May 30.

She urged Guangzhou residents to strictly abide by relevant policies and measures introduced by provincial and city governments to curtail the COVID-19 outbreak and asked people to avoid travel outside Guangdong if it's not essential that they do.

Guangdong reported four new locally transmitted confirmed COVID-19 cases plus another two from previously identified asymptomatic carriers on Wednesday, according to a statement released by Guangdong Health Commission on Thursday. All the cases were found in Guangzhou, the statement said.

Meanwhile, the city reported three confirmed cases that were imported, including two from Malaysia and one from Bangladesh, plus another 10 imported asymptomatic carriers on Wednesday.

As of Wednesday, Guangdong has reported a total of 2,582 confirmed cases, including 1,059 imported ones. Some 170 patients remain hospitalized.