AKIPRESS.COM - One of the vehicles exploded in the attack, which happened on Thursday morning, state news agency Xinhua said.

An "unknown number of people were killed and injured", with people rushed to several hospitals, Xinhua added.

There are periodic outbreaks of violence in Xinjiang, which is home to the Muslim Uighur minority group.

Last month a bomb attack at a station in Urumqi killed three people and injured dozens more. China blamed the attack on Uighur separatists.

Information about incidents in the region, where ethnic tensions rumble between Uighurs and Han Chinese, is tightly controlled.

Pictures on weibo - China's equivalent of Twitter - taken by eyewitnesses appeared to show that Thursday's attack happened at one end of a busy market street lined with stalls selling vegetables.

"Witnesses said two cross-country vehicles driving from north to south ploughed into people in the market at 07:50. Explosives were thrown out of the vehicles," the Xinhua report said.

One photo showed flames engulfing a junction and others showed at least three fire engines mobilised to put out the fire.