Stricter control and prevention measures have been introduced to fight COVID-19 in Shenzhen, Guangdong province, as the southern metropolis remains at high risk of community transmission, a senior official said on Monday.

Huang Qiang, deputy secretary-general of the Shenzhen municipal government, said the number of infections reported in Shenzhen has spiked again.

"The number of the cases detected in the city's key areas and groups continued to grow, with small cluster infections having been reported in urban villages and factories," Huang said at a news conference.

"These indicate we still need to introduce and implement strict measures in advance to guard the city against the pandemic," he said.

Huang did not rule out the possibility of a rise in infections in the city in the weeks to come, given the expanded testing in the city which borders the Hong Kong Special Administrative Region.

To curb the spread of the coronavirus in the city, the local government has ordered all officials and employees to work from home except for those involved in epidemic control and necessary public services.

The city's third round of citywide testing was launched on Monday, he said.

Xu Wei, deputy director of the Shenzhen Transportation Bureau, said all subway and bus services in the city have been suspended from Monday to Sunday.

"Residents can book online for car-hailing and taxi service if they need to go out, or they can dial the 120 hotline for help in case of emergency," Xu said.

Lin Hancheng, an inspector for the Shenzhen health commission, said the operations of major hospitals and medical institutions in the city will not affected.

"No medical institutions are allowed to refuse patients on any pretext," he said.

Mo Xiling, deputy director of Shenzhen's market regulation administration, said the city's supplies of meat, eggs, vegetables, milk and subsidiary food are adequate and prices remain stable.

Meanwhile, the Dongguan city government has launched multiple rounds of citywide testing on Monday to identify possible COVID-19 patients and asymptomatic carriers.

Large-scale conferences, events, forums, performances, sales promotions, square dances and gatherings have been suspended, and all commercial entertainment venues have been temporarily closed in the city.

According to the Guangdong Health Commission, the province reported 79 locally transmitted confirmed cases and 151 local asymptomatic carriers on Sunday. Of those, Shenzhen reported 75 confirmed cases and 11 asymptomatic carriers. Neighboring Dongguan confirmed two cases and 140 asymptomatic carriers.