A fatal vehicle crash in Beijing's Tian'anmen Square was planned by a Uyghur separatist group, designated as a terrorist organization by the US and UN, said China's top security official, Meng Jianzhu.

An SUV ploughed through bystanders in the capital's iconic Tian'anmen Square on Monday and burst into flames, killing the three people in the car and two bystanders.

Beijing police have arrested five suspected radical Islamists. Security has been strengthened in both Beijing and in Xinjiang.

Meng Jianzhu, chief of the Commission for Political and Legal Affairs of the Communist Party of China Central Committee, blamed the incident on the "East Turkistan" forces.

"This violent terrorist incident that's happened in Beijing was organised and premeditated," Meng told Hong Kong's Phoenix TV.

"We must seek to further strengthen international anti-terror cooperation...in order to create a strong deterrent and further safeguard peace and stability in our region," Meng said on the sidelines of a Tashkent meeting of the Shanghai Cooperation Organization (SCO).

During talks with Zhang Xinfeng, director of the executive committee of SCO's Regional Anti-Terrorism Agency, Meng said many countries, including China, were currently under threat amid rising global terrorist activities and China was more determined to fight against violence and terrorist crimes.

Zhang strongly condemned the terrorist attack, which caused civilian casualties, saying the executive committee would fully support a thorough investigation into the case.

The UN and US placed the "East Turkistan" forces on lists of terrorist organizations after the Sept 11, 2001 attacks.