China's top security official has named an Islamic movement as "behind-the-scenes supporters" of this week's fatal attack in Tiananmen Square, in Beijing's first claim of an organised link to the incident.

"Its behind-the-scenes supporters were the terrorist group the East Turkestan Islamic Movement (ETIM) based in Central and West Asia," Meng Jianzhu said when asked about the Tiananmen incident on a visit to Tashkent in Uzbekistan, video posted online Thursday showed.

A high-profile car crash on Monday killed two tourists and injured dozens at the popular site and symbolic heart of the Chinese state. The three people in the car -- a man, his wife and his mother -- all died in the crash, police say.

They said the vehicle had a licence plate from Xinjiang, the far western region where China's mostly Muslim Uighur minority is concentrated, while the names released of the three people inside and five other detained suspects sounded Uighur.

ETIM is known as a militant Islamic separatist group that seeks an independent state in Xinjiang.

Foreign ministry spokeswoman Hua Chunying on Friday called the group "the most immediate and realistic security threat in China".

It and other organisations "have long been engaged in central, east and west Asia, and have colluded with other international terrorist organisations", she said at a regular press briefing, without elaborating or confirming any ETIM tie to the attack.

The United States and the United Nations both classified ETIM as a terrorist organisation in 2002, during a period of increased US-Chinese cooperation following the 9/11 attacks.

But ETIM's strength and links to global terrorism are murky. Some experts say China exaggerates its threat to justify tough security measures in Xinjiang, which has seen sporadic ethnic clashes and anti-government sentiment.

During his visit, Meng called China -- along with other nations -- a victim of the rising global terrorism threat, which it would further resolve to combat, the official Xinhua news agency reported.

He made his comments, a video of which was posted on the Chinese web portal Tencent, while visiting an anti-terrorism office of the Shanghai Cooperation Organisation, a regional security group which links China, Russia and a number of central Asian countries.

ETIM may have ties in Pakistan and central Asian countries, but it is unclear how close they might be, said Michael Clarke, a professor at Griffith University in Sydney who has authored a book on China's policy of integration in Xinjiang.

"It's not that China shouldn't be concerned about those (ties), but the core issue is that the linkages have been exaggerated by the Chinese government," he said, adding that he was "sceptical on the exact nature" of ETIM.

Chinese state-run media have reported periodic bouts of violence in Xinjiang which Beijing often describes as "terrorist attacks".

One such incident in June left 35 people dead, and 139 people have been arrested in recent months for spreading jihadist ideology.

But Uighur organisations dismiss claims of terrorism and separatism as an excuse by Beijing to justify religious and security restrictions.

Information in the area is difficult to independently verify.

Alim Seytoff, a spokesman for the overseas-based World Uyghur Congress, said Uighurs face close security scrutiny in Xinjiang and he does not believe an organised resistance movement exists there.

Beijing says its policies and investment in Xinjiang have brought tremendous development.

The region's economy grew 10.8 percent to 570 billion yuan ($94 billion) in the first nine months of 2013 -- 3.1 percentage points above the national rate and the ninth-highest increase in the country, according to the Xinjiang government news portal Tianshan.

Critics counter that the economic growth mostly benefits an influx of ethnic majority Han Chinese, millions of whom have moved to the resource-rich region.

Ethnic frictions have risen in Xinjiang as a result, and rioting in the capital Urumqi involving both ethnic groups in 2009 left around 200 people dead.

The state-run Global Times on Friday warned against using the Tiananmen incident to discriminate against Uighurs, Xinjiang or Islam and causing the ethnic group "yet another round of injury", in an editorial that only ran in Chinese.

Uighurs attending Friday prayers at the capital's oldest mosque were reluctant to speak about the event, with some professing not to have heard of it.

Others condemned the incident, while a student who declined to be named said the overwhelming majority of Uighurs opposed terrorism.

"Just a few do it," he said.