Chinese police announced Wednesday they have captured five suspects over a "terrorist attack" in Beijing's Tiananmen Square, the first time authorities have accused terrorists of striking in the capital.

The driver of the sports utility vehicle which sped along the pavement, ploughed into crowds and crashed in the symbolic heart of the Chinese state on Monday was named by state media as Usmen Hasan.

His wife and mother were both with him, the media said.

City police said on a verified social media account that they "ignited the petrol inside the car so the car caught on fire" and the three "died at the scene".

Two tourists, one a woman from the Philippines, were also killed in the incident, close to a huge portrait of Mao Zedong hanging from the walls of the Forbidden City, and 40 people were injured, according to police.

It was a "carefully planned, organised and premeditated violent terrorist attack", the police statement said, adding that the car carried petrol, knives and banners bearing extremist religious content.

Police said the vehicle had a licence plate identifying it as from the restive western region of Xinjiang, home to the mostly Muslim Uighur minority.

The names given for the three dead family members and the five detained suspects sounded Uighur, although their ethnicities were not explicitly stated.

The five people were arrested on Monday and confessed to plotting the "attack", police said, adding that "jihad banners", long knives and other items were found in at least one suspect's residence.

At least one of those held was from Lukqun, where state media said 35 people were killed in June in what Beijing called a "terrorist attack".

The police account of a terrorist strike in the heart of the capital prompted fearful reactions from residents of the city.

"I work in Beijing. I never imagined there would be an act of terror this close to us," one user of Sina Weibo, a Chinese equivalent of Twitter, wrote.

Another said: "I suddenly feel that life is much harder."

Beijing has blamed Uighur groups for what it calls "terrorist" attacks in the far west, but details of alleged incidents are hard to confirm. Exile groups accuse China of exaggerating the threat to justify religious and cultural restrictions.

The police description of the suspects as being found with extremist religious materials closely mirrored descriptions of those arrested over previous Xinjiang "terrorist attacks". Rights groups say those accounts have led to brutal crackdowns on Uighurs.

No Uighur group has claimed responsibility for Monday's crash.

"There are extreme worries over the fate of Uighur people," said Dilshat Rexit, a spokesman for the World Uyghur Congress, an exile group which Beijing has condemned as separatist, after news of the detentions emerged.

"The Beijing incident is an excuse for repressing Xinjiang," he said in a statement. "China is increasing its surveillance of Uighur students and business people, and has instituted discriminatory policies sending people back to Xinjiang.

"According to local sources, 93 Uighur people have been arrested in Beijing, the secret service is carrying out checks, and has provided no reasons for the arrests."

Earlier the group's president Rebiya Kadeer said: "Today, I fear for the future of East Turkestan and the Uighur people more than I ever have."

East Turkestan is the name which the activist organisation uses to refer to Xinjiang, where Uighurs make up 46 percent of the population.

The group added that it fears the response by authorities in Beijing will "lead to further demonisation of the Uighur people and incite a fierce state crackdown" in Xinjiang.

Xinjiang is a sparsely populated but strategically important area which borders several central Asian countries. It is periodically hit by violent clashes, including riots in the region's capital Urumqi in 2009 which left around 200 dead, but information is often hard to obtain.

Police have arrested at least 139 people in Xinjiang in recent months for allegedly spreading jihad, according to state-run media.

In August state-run media said that a policeman had been killed in an "anti-terrorism" operation -- although overseas reports said 22 Uighurs died in the incident.

Three Philippine tourists and one Japanese were among the injured on Monday.

"All patients involved in the incident are recovering," a nurse who declined to be named told AFP at Beijing's Tongren hospital, where Philippine officials said the injured were being treated.