Ahead of China's 70th anniversary on Oct. 1, 2019, Hong Kong protesters have begun putting out a new message: Tuck their shirts in, so as to expose undercover police in their midst.

The message was spread on multiple social media platforms, and appeared to be premised on the claim that such a move would make it harder for undercover police to conceal revolvers or batons that they might be carrying on their bodies.

Everybody tuck in your shirt to identify the Hong Kong police pretend fake protestor that carrying real gun and baton on their waist. #HongKong #HongKongProtestors #AntiExtraditionBill #help #sos #HongKongHumanRightsandDemocracyAct pic.twitter.com/qB3Q1AajmG

— Funny Joint (@funny_joint) September 30, 2019

As more #HK police disguised as #antiELAB protesters, and most tucked their batons & guns into their pants, @lihkg_forum user urges frontliners to tuck their shirts in in the upcoming protests to show that they’re not moles. #Hongkong wisdom 😂 pic.twitter.com/6P8heAgbCF

— Michele Fan (@wingp) September 29, 2019

For celebrate 1st Oct 🇨🇳🇨🇳🇨🇳🇨🇳🇨🇳
HongKong Protesters please tuck in your tops so police spies can’t hide their batons #SaveHK #FightForFreedom @realDonaldTrump @VP @robert_spalding @Jkylebass @YatesDCIA @marcorubio @SecPompeo @SpeakerPelosi @SenRickScott @SolomonYue pic.twitter.com/igdjKUUYW0

— G嘜 (@hillhill_g) September 30, 2019

全民攝衫！

To avoid some doggie pretend to be human, we are going to tuck in our t-shirt tomorrow.#HongKongProtests #HongKongProtester #HongKong #HKers pic.twitter.com/HNLlOPGCRx

— SuperBigPiece😷 (@superbigpiece) September 29, 2019

Translation:"All residents, tuck in your shirt!"

The protesters have drawn inspiration from the “Four Heavenly Kings of Canto-pop”.

A picture taken in the 1990s showed the four singers -- Leon Lai Ming, Aaron Kwok Fu-shing, Jacky Cheung Hok-yau and Andy Lau Tak-wah -- all had tucked their shirts in.

Allegedly undercover police fired live round into the air

The South China Morning Post (SCMP) noted that the message came in the wake of an incident on Sep. 29, in which a Hong Kong police officer, who was supposedly undercover, fired a live round into the air at Wan Chai, while clashing with protesters.

The officer had purportedly been wearing balaclavas similar to that of the protesters.

While the Hong Kong police did not clarify if he had been undercover, they explained that the police's rationale for firing the warning round was for the safety of his colleagues who were surrounded and attacked by protesters.

The police said: "Some police officers were surrounded and attacked by a large group of violent protesters. With their lives under serious threat, an officer fired one warning shot into the sky to protect their own safety."

SCMP further noted some protesters have also called for people to roll up their trousers, on the assumption that there could be police hiding guns around their ankles as well.

Protests planned in six districts on China's National Day

Bloomberg further reported that thus far, protesters have planned afternoon rallies in six districts that have seen some of the worst violence.

Meanwhile, the Hong Kong police have stated that a "very violent attack" is expected for China's National Day, as protesters "are increasingly resorting to terrorism", both The Straits Times and Reuters reported.

As per John Tse, the chief superintendent of the Hong Kong police's public relations branch:

"After our analysis, we're expecting the situation tomorrow to be very, very dangerous. Core rioters are increasing their violence. The depth and breadth of their violence and plans show that they are increasingly resorting to terrorism."

The Hong Kong authorities have been highlighted as especially keen to avoid incidents that could embarrass the central Chinese government in Beijing.

As such, a total of 157 people, including 67 students, have been arrested over the weekend of Sep. 28 and 29.

The police also stated that eight officers were injured, amidst clashes that saw protesters set fire and throw petrol bombs, while the police fired tear gas and water cannons.

In the meantime, Reuters further highlighted that China has also doubled its troop levels in the city, largely consisting of the largest active People's Liberation Army (PLA) force ever seen in Hong Kong.

What's more, this increase also includes elements from the People's Action Police (PAP), a paramilitary specifically geared towards handling internal security and riots.

Top image collage from Danny Joint Twitter