China has staged another drill aimed at Hong Kong’s protesters, this time near the border of the former British colony in the mainland city of Shenzhen, involving 20,000 police from across Guangdong province.

They gathered on Tuesday in a public square in the city’s Baoan district and mocked a crackdown against rioters.

Photos and videos of the drill show officers carrying shields and batons and hurling tear gas canisters at others acting as protesters and dressed in black, the prevailing color at Hong Kong’s ongoing rallies against a now suspended China extradition bill.

Shenzhen papers noted that the entire drill was commanded by a deputy mayor in charge of public security, which simulated a group of masked “rioters” charging police cordons, throwing makeshift bombs and explosives and ramming a burning dump truck against a government building.

Riot police then unfurl warning flags before firing pepper spray and tear gas. At one point, they deploy police dogs to scare off the “protesters.”

Water cannons, bomb disposal vehicles, hazardous chemical disposal vehicles and other vehicles were also deployed.

The day-long drill was live-streamed on the websites of the Shenzhen police and a news website under the Chinese Ministry of Public Security, and was watched by 500,000 people.

On Monday, another batch of officers were involved in a smaller sea-air exercise in Shenzhen Bay across from Hong Kong’s New Territories. They boarded helicopters and speedboats and patroled the area. A dozen armored vehicles and constables in full riot gear were also seen near a checkpoint on the Hong Kong border.

Shenzhen’s municipal government noted in a gazette that the drill was held to coordinate security and deployment for the big celebrations on the 70th anniversary of the Communist republic on October 1.

“The drill will hone skills and resolve of our policemen, in a show of force to our people the police’s capabilities to safeguard stability,” read the gazette.

Helicopters and speedboats could be seen in Hong Kong across Shenzhen Bay.

The Shenzhen drill came hot on the heels of a previous exercise in the neighboring city of Foshan, and it was reported that Guangdong authorities would mobilize about 160,000 officers in a week-long event to heighten moral and deterrence.

The Shenzhen war-game was also closely watched in Hong Kong, a city still reeling from a strike as well as clashes the day before. Some think the “rioters” in Shenzhen were mimicking Hong Kong demonstrators.

Yet observers say the Basic Law has no provisions enabling the police force in a mainland city to cross the border and enforce the laws in Hong Kong, as only Chinese troops already stationed in the city can be moblized when asked by the Hong Kong government and approved by Beijing.

Meanwhile, the Hong Kong Police Force issued a short statement on Tuesday refuting rumors that some People’s Liberation Army troops, either from barracks in the city or from across the border, have reinforced the city’s beleaguered police force and posed as local officers to quell widespread demonstrations. The statement said the rumors were “totally unfounded.”

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