Troops from the Hong Kong garrison of the People’s Liberation Army tested their ability to intercept fugitives trying to flee by boat in a drill in the city on Tuesday.

The exercise involved ground, navy and air force personnel and was staged at a sensitive time – the same day Beijing’s top legislative body passed a controversial national security law for Hong Kong.

Special troops, air defence soldiers, warships and aircraft carried out maritime and island searches to “comprehensively test the Hong Kong garrison’s defence capabilities”, according to state broadcaster CCTV.

“We aimed to track down the fugitive in the first attempt and intercept the suspect,” one of the PLA soldiers told the broadcaster.

Nearly two minutes of footage aired in the report showed military personnel stopping and searching a vessel, using helicopters to locate fugitives after they left their boat and fled to an island, and apprehending them.

There was also a search and rescue operation, and a joint air and sea patrol was conducted in Victoria Harbour after the drill, the footage showed.

The state broadcaster said the PLA garrison had also vowed to defend the “one country, two systems” framework to safeguard security and peace in Hong Kong.

It came the same day the National People’s Congress Standing Committee in Beijing unanimously approved a law for Hong Kong that prohibits acts of secession, subversion, terrorism and collusion with foreign forces to endanger national security.

The law, which has drawn international condemnation, is expected to take effect on Wednesday, the 23rd anniversary of Hong Kong’s handover to China from British rule.

Drills carried out by the PLA’s Hong Kong garrison have drawn attention since anti-government protests began in the city last summer, and they have been seen as sending a warning to potential separatists. On Sunday, official newspaper PLA Daily released a video of sharpshooters taking part in intensive live-fire drills and sniper training at an unidentified firing range in Hong Kong.

Footage of the training, which reportedly took the form of a shooting contest, also showed soldiers crawling with their rifles and shooting while lying on a swinging board. A senior officer in the video said the drills were designed to get shooters prepared for “actual combat”.