On Monday, the 62-year-old man surnamed Fan ploughed a small SUV through a gate to the complex in the city of Zhuhai and into crowds of people as they exercised on the roads inside, according to police.

An initial police statement said people had been injured, but did not mention any deaths -- and videos of the attack later appeared to be scrubbed from China's tightly controlled social media platforms.

As of Wednesday, the rampage had left 35 people dead and 43 with injuries not deemed life-threatening, according to state media reports.

AFP witnessed residents and delivery drivers laying bouquets at a gate outside the complex on Wednesday morning, before the flowers were carried behind a cordon fence within minutes.

"What happened wasn't a small incident," a woman of about 50 told AFP, requesting anonymity to protect her privacy.

"We should remember those who passed away and not be so cold. I think more people in Zhuhai should come out here and lay some flowers in memorial," she added.

- Divorce 'dissatisfaction' -

Police said Fan was apprehended at the scene but was in a coma after self-inflicted knife injuries, preventing them from interrogating him.

But the force said preliminary enquiries suggested the attack was "triggered by (Fan's) dissatisfaction with the division of property following his divorce".

Security at the scene was tight on Wednesday, with plainclothes officers using their bodies and umbrellas to block AFP reporters from taking photos and videos.

Since Tuesday night, journalists had observed people placing candles and flowers near the site of the attack to commemorate the victims.

But cleaning staff removed the memorials in the early hours of Wednesday, with some telling AFP they were acting on an "order from the top".

Officials at the site said the items were being moved to a "mourning hall" inside the complex, with no access to the public.

Footage of Monday's incident geolocated by AFP showed people lying motionless on the ground, while others were seen frantically attempting to resuscitate the seemingly unconscious.

An eyewitness surnamed Liu told Chinese news magazine Caixin that the car "drove in a loop" around a dedicated exercise track encircling the stadium in the sports complex.

"People were hurt in all areas of the running track -- east, south, west, and north," he said.

Chinese President Xi Jinping urged "all-out efforts" to treat the injured and "demanded punishing the perpetrator in accordance with the law", according to state news agency Xinhua.

The incident took place as Zhuhai hosts China's largest airshow, showcasing Beijing's civil and military aerospace sector.

- Spate of mass killings -

Violent crime is generally rare in China compared to many Western countries, but the Asian nation has witnessed a spate of deadly attacks in recent months.

In several cases, Beijing has described the killings as isolated incidents, or the motives of the perpetrators have not been publicly disclosed.

After the Zhuhai attack, Xi called on authorities to "strictly guard against the occurrence of extreme cases", Xinhua reported.

Japan's embassy warned its citizens in China to be on high alert and "refrain from speaking loudly in Japanese", despite no initial indications that any had been targeted.

In September, a Japanese schoolboy was fatally stabbed in the neighbouring city of Shenzhen, prompting an outcry from Tokyo.

A man killed three people and wounded 15 in a knife attack at a supermarket in Shanghai in October, while in July, police said a vehicle crashed into pedestrians in the central city of Changsha, killing eight.

Monday's incident is on a par with some of China's deadliest attacks in recent memory.

In 2014, 31 people were killed and 143 were wounded in a knife attack at a railway station in the southwestern city of Kunming that officials later blamed on terrorism.

The same year, a vehicle ramming and suicide bombing in the northwestern city of Urumqi killed 43 -- including four assailants -- and wounded more than 90. The incident was also deemed a terror attack.