China’s state media has said that a military intervention in Hong Kong is “at Beijing’s disposal”, but rejected the suggestion that it would mean a repeat of scenes from the 1989 Tiananmen Square massacre.

An editorial for the Communist Party-run Global Times tabloid confirmed that paramilitary training exercises being staged near the border with Hong Kong should be seen as a “clear warning” to protesters, whom the newspaper dubbed “rioters”.

On Friday, Chinese forces were seen marching and taking part in crowd-control drills using riot shields, manoeuvring between barricades set up on the sports field at an arena in Shenzhen, some 30km (19 miles) from Hong Kong city centre.

It was the second day of drills that began on Thursday and led the US national security adviser John Bolton to warn China that “it would be a big mistake to create a new memory like [Tiananmen Square] in Hong Kong”.

Mr Bolton told VOA News that “people in America remember” the massacre on 4 June 1989 when Chinese soldiers opened fire on student protesters in Beijing, with estimated death tolls ranging from several hundred to “at least 10,000”.

Continuing protests rock Hong Kong: In pictures Show all 35 1 /35 Continuing protests rock Hong Kong: In pictures Continuing protests rock Hong Kong: In pictures Police officers point their guns towards pro-democracy protesters after a clash at a march in Hong Kong on August 25 Reuters Continuing protests rock Hong Kong: In pictures Pro-democracy protesters throw molotov cocktails during clashes with riot police in Hong Kong on August 25 Reuters Continuing protests rock Hong Kong: In pictures Demonstrators rally behind barricades ass they are shrouded in tear gas deployed by police in Hong Kong on August 25 Reuters Continuing protests rock Hong Kong: In pictures Police clash withpro-democracy protesters at a march in Hong Kong on August 25 Reuters Continuing protests rock Hong Kong: In pictures A police officer prepares to strike a protester as clashes erupt during a pro-democracy march in Hong Kong on August 24 AFP/Getty Continuing protests rock Hong Kong: In pictures A water cannon is fired by riot police to clear the street of demonstrators during a protest in Hong Kong on August 25 EPA Continuing protests rock Hong Kong: In pictures Pro-democracy protesters use a slingshot during clashes with riot police in Hong Kong on August 25 Reuters Continuing protests rock Hong Kong: In pictures Riot police fire tear gas to disperse pro-democracy protesters in Hong Kong on August 24 Reuters Continuing protests rock Hong Kong: In pictures A demonstrator throws a molotov cocktail as they clash with riot police during a protest in Hong Kong on August 25 Reuters Continuing protests rock Hong Kong: In pictures A demonstrator swings a tennis racket in an attempt to knock back a tear gas cannister thrown by riot police during a protest in Hong Kong on August 25 Reuters Continuing protests rock Hong Kong: In pictures A protester displays a Hong Kong Independence flag during a pro-democracy march in Hong Kong on August 24 EPA Continuing protests rock Hong Kong: In pictures Riot police tend to a detained demonstrator who has been injured during a protest in Hong Kong on August 25 Reuters Continuing protests rock Hong Kong: In pictures A demonstrator uses bamboo poles to build a barricade during a protest in Hong Kong on August 25 Reuters Continuing protests rock Hong Kong: In pictures Riot police clash with demonstrators during a protest in Hong Kong on August 24 Reuters Continuing protests rock Hong Kong: In pictures Protesters are hit by tear gas fired by the police in Hong Kong on August 24 AFP/Getty Continuing protests rock Hong Kong: In pictures Demonstrators shrouded in tear gas shield themselves behind barricades during a clash with riot police in Hong Kong on August 25 Getty Continuing protests rock Hong Kong: In pictures Riot police arrest a protester during a pro-democracy march in Hong Kong on August 24 EPA Continuing protests rock Hong Kong: In pictures Police clash with pro-democracy protesters at the Hong Kong international airport on August 13 AFP/Getty Continuing protests rock Hong Kong: In pictures Protesters fall back as they clash with police during a protest at Kowloon Bay in Hong Kong on August 24 AFP/Getty Continuing protests rock Hong Kong: In pictures Police clash with pro-democracy protesters at the Hong Kong international airport on August 13 Reuters Continuing protests rock Hong Kong: In pictures Riot police move to disperse protesters during a clash at the Hong Kong international airport on August 13 Reuters Continuing protests rock Hong Kong: In pictures Commuters riding in a bus drive past protesters in Hong Kong's Kowloon Bay on August 24 AFP/Getty Continuing protests rock Hong Kong: In pictures Protester hold umbrellas as they take part in a pro-democracy march in Hong Kong on August 24 EPA Continuing protests rock Hong Kong: In pictures Riot police detain a demonstrator as they clash during a protest in Hong Kong on August 24 Reuters Continuing protests rock Hong Kong: In pictures Pro-democracy protesters block the entrance to the airport terminals after clashes with police at the Hong Kong international airport on August 13 AFP/Getty Continuing protests rock Hong Kong: In pictures Riot police spray pepper spray as shield themselves by a police van during a clash with pro-democracy protesters at the Hong Kong international airport on August 13 Reuters Continuing protests rock Hong Kong: In pictures Riot police use pepper spray to disperse protesters during a demonstration at the Hong Kong international airport on August 13 Reuters Continuing protests rock Hong Kong: In pictures Demonstrators shrouded in tear gas shield themselves behind barricades during a clash with riot police in Hong Kong on August 25 Reuters Continuing protests rock Hong Kong: In pictures Medical professionals gather to protest police brutality at the Queen Elizabeth Hospital in Hong Kong on August 13 Getty Images Continuing protests rock Hong Kong: In pictures Police detain a pro-democracy protester at the Hong Kong international airport on August 13 AFP/Getty Continuing protests rock Hong Kong: In pictures A protester is halted by police during an occupation at the Hong Kong international airport on August 13 AP Continuing protests rock Hong Kong: In pictures Police clash with pro-democracy protesters at the Hong Kong international airport on August 13 AFP/Getty Continuing protests rock Hong Kong: In pictures Police stand guard at the entrance of the departure terminals at the Hong Kong international airport on August 13 AFP/Getty Continuing protests rock Hong Kong: In pictures Protesters continue their occupation at the Hong Kong international airport on August 14 AP Continuing protests rock Hong Kong: In pictures Travellers read placards and posters left by pro-democracy protesters at the Hong Kong international airport on August 14 AP

In Shenzhen, police could be seen from a distance conducting drills in military fatigues, using shields, poles and other riot-control gear.

In one exercise, two groups marched in formation with those in front raising shields as if to protect themselves from projectiles. Others behind held red flags and banners. The words “the law” and “prosecuted” could be seen on one, the Associated Press reported.

Outside, dozens of armoured personnel carriers and trucks sat in a car park of the Shenzhen Bay stadium, close to a bridge linking mainland China to Hong Kong.

In its editorial, the Global Times said China was a “much stronger and more mature” country since 1989, and that “its ability to manage complex situations has been greatly enhanced”.

Chinese servicemen attend a crowd control exercise at the Shenzhen Bay stadium on Friday (Reuters)

It warned Washington against trying to “intimidate China” with references to events 30 years ago and said it was hoped that Hong Kong can “actively restore the rule of law under the leadership of [Carrie Lam’s devolved] HKSAR government”.

Nonetheless, it said: “If Hong Kong cannot restore the rule of law on its own and the riots intensify, it’s imperative then for the central government to take direct actions.”

Protests in Hong Kong started slowly at the start of the year as a defiant response to a new extradition bill, which would have made it easier for criminal suspects to be deported to the mainland and elsewhere on a case-by-case basis.

Critics said the new law would have made it easier for Beijing to persecute political enemies in the city, and it was shelved after more than a million people marched in demonstrations on two consecutive Sundays.

As the protests have grown increasingly violent in the past 10 weeks, however, the unrest has become a general pro-democracy movement in defence of Hong Kong’s much-prized autonomy. Police have been accused of using a heavy-handed approach in some incidents.

The demonstrators are now demanding expanded political rights, the complete withdrawal of the extradition bill and the resignation of chief executive Ms Lam, among other things.

Meanwhile on Friday, the chief executive of Hong Kong’s flag carrier airline Cathay Pacific resigned following pressure by Beijing over participation by some of its employees in the anti-government protests.

Cathay Pacific said Rupert Hogg resigned “to take responsibility” following “recent events”.

The company chair, John Slosar, said in a statement the airline needed new management because events had “called into question” its commitment to safety and security.