Explosives hurled from two vehicles which rammed an open market in China's western region of Xinjiang killed and wounded an unknown number of people on Thursday, the official Xinhua news agency and a witness said.
China has blamed a series of knife and bomb attacks in recent months on separatist militants from Xinjiang, the traditional home of the ethnic Muslim Uighurs.
The cross-country vehicles rammed into shoppers in an open market in the Xinjiang capital, Urumqi, Xinhua reported, citing witness reports. Explosives were flung out of the vehicles, and one of the vehicles exploded.
A business owner told Xinhua he had heard a dozen big bangs.
The blasts occurred at an open air morning market near Renmin Park in downtown Urumqi. Flames and heavy smoke were seen nearby while the area had been cordoned off after the blast.
Xinjiang has been plagued by violence for years, but rights activists and exile groups say the government's own heavy handed policies in the region have sowed the seeds of unrest.
Photos posted on social media purportedly of the blast, but unverified by Reuters, showed a column of smoke and chaos at the market, with bloodied people lying on the tree-lined road near small stands selling fruit, vegetables and eggs.
"There were two vehicles that drove like crazy toward the morning market ... there were definitely people killed," a witness who declined to give his name told Reuters by telephone.
"The market was total chaos, hawkers and shoppers started running everywhere... it was definitely a terrorist act. I'm so angry."