A "terrorist attack" in Beijing's Tiananmen Square, the symbolic heart of the Chinese state, represents an embarrassing failure for the nation's vast police and intelligence apparatus and shows it cannot plug all security vulnerabilities, analysts say.

Communist China spends vast sums on ensuring order among a population of 1.35 billion people, more even than on its military, the world's largest.

Tiananmen, in the middle of the sprawling Chinese capital, has long been a magnet for protests both large and small, including the huge pro-democracy demonstrations of 1989 that challenged Communist Party rule.

The square is permanently under heavy security with uniformed and plainclothes police constantly on the lookout for any sign of trouble, though the spectre of a terrorist attack in the centre of Beijing raises the stakes significantly.

"Clearly the party will be horrified", David Tobin, a University of Glasgow expert on Chinese politics, told AFP. "This is a highly policed region. You wouldn't think that something like this would happen here. So this will make the party nervous."

The three people in the car which crashed on Monday, all of whom died, were from the same family, Beijing police said Wednesday, and another five people had been arrested.

It was a "carefully planned, organised and premeditated violent terrorist attack", they added -- the first time authorities have admitted to such a strike taking place in the capital.

The names released for the dead and the apprehended suspects appear to belong to members of China's mainly Muslim Uighur minority, though police and media refrained from explicitly stating their ethnicity.

The car was licensed in China's far western region of Xinjiang, home to most of China's Uighurs, many of whom say they are victims of discrimination and ethnic profiling by the state, and the scene of periodic unrest.

Willy Lam, a China expert at the Chinese University of Hong Kong, said that as well as the fact security measures were proven ineffective, the deadly nature of the incident in which at least one foreigner died compounded the embarrassment.

"It's a big loss of face for the authorities," he said, noting that the crash came ahead of a key Communist Party meeting set for next month in Beijing.

Attack could embolden others

China's declared domestic security budget across all levels of government is 769 billion yuan ($126 billion) this year, more than the country officially plans to spend on its armed forces, and an increase of more than 200 billion yuan since 2010.

"If the Chinese MPS (Ministry of Public Security) cannot secure Tiananmen, it shows that China, as a whole, is insecure, inviting more challenges," Kam C. Wong, a former Hong Kong police official who teaches criminal justice at Xavier University in the United States, wrote in an email.

The exact motivation for the mayhem in which a sport utility vehicle left the major transport artery that runs in front of the Forbidden City -- a former imperial palace -- and rammed into a crowd of tourists and police, killing at least two visitors and injuring dozens, remains murky.

Experts have cautioned against jumping to conclusions about the nature of the incident given the government's virtual monopoly on what information is released.

"It's the fact that it occurred in Tiananmen Square that immediately gives rise to suspicion of something of a political nature," said John Delury, an expert on modern Chinese politics at Yonsei University in Seoul.

But given that Xinjiang has been a hotbed of tensions in recent years -- about 200 people died in riots in its capital Urumqi in 2009 -- the region also cannot be discounted as a source of violence.

"I think the fact that it could take place in Beijing shows that there are limits as to what the police can do if there is a high degree of resistance against China's fundamental policy towards the Uighurs," Lam said.

"There is no police regime in the world which is effective if there is massive resistance from one sector of the people."

Tobin, who focuses on identity politics in Xinjiang and says the issue can only be understood as a problem that has existed for more than two centuries, pointed out that the crash appeared unsophisticated and was unlikely to suggest any transnational terror links.

"From looking at what happened it certainly doesn't look like the type of incident we see across the Middle East with sophisticated technology, lots of coordination," he said.

"It seems quite crude, driving a jeep into people and then setting liquid on fire to make the jeep go alight, so there doesn't seem to be any evidence of a sort of global network of terrorism there. It could be disgruntled individuals."

The conflagration at Tiananmen will likely lead to intensified security measures against Uighurs in both Beijing and the far west, analysts said. A Uighur rights group has already expressed fears of a crackdown.

But Wong warned that control regimes, no matter how good, will always be vulnerable in the face of suicide attackers.

"Simply, people cannot be deterred if they are not afraid to die," he said.