Urumqi blast
Policemen from the Special Weapons and Tactics (SWAT) team practice during a drill in Urumqi, Xinjiang Autonomous Region, in this file photo.Reuters

A blast in the Chinese province of Xinjiang has killed 31 people and injured more than 90, local television channels report.

Two vehicles rammed into the crowd at a market in the provincial capital Urumqi early on Thursday and the assailants threw explosives, the official Xinhua news agency said. One of the vehicles involved in the attack exploded.

China's Ministry of Public Security said the latest Xinjiang attack was a "violent terrorist incident".

Tensions in the western province of Xinjiang have been on the rise since the 2009 clashes between ethnic Uighurs and the majority Han Chinese. More than 200 people were killed in the riots.

Beijing, which accuses the Uighurs of terrorism and a separatist agenda, tightened security measures in the remote, resource-rich Xinjiang region.

The Chinese government tightly controls information from the violence-hit far western region. The country's official news agency said in the morning that "an unknown amount of people" were injured in the blast.

Later, state broadcaster Central Television said at least 31 people were killed.

However, Weibo (the Chinese equivalent of Twitter) displayed messages and pictures of the blast.

"There were multiple strong explosions in the morning market at the Cultural Palace in Urumqi ... I saw flames and heavy smoke as vehicles and goods were on fire while vendors escaped leaving their goods behind," a Weibo user posted.

In April, Urumqi witnessed a deadly knife attack that coincided with the visit of President Xi Jinping to the region. Also in April, a bomb attack at the railway station killed three people and injured dozens. Beijing blamed Uighur militants for the attacks.

In March, suspected Uighur militants stabbed to death 29 people and wounded 143 at a railway station in the south-western city of Kunming.