Police officers stand guard near a blast scene, which has been cordoned off, in downtown Urumqi, capital of northwest China's Xinjiang Uygur Autonomous Region, May 22, 2014. [Photo/Xinhua]

URUMQI - The explosions at an open air market in Urumqi, capital of northwest China's Xinjiang Uygur Autonomous Region, have left 31 dead and more than 90 injured Thursday, authorities said. The blast is a "serious violent terrorist incident", China's Ministry of Public Security said in a statement on Thursday.

Chinese President Xi Jinping pledged to severely punish terrorists and spare no efforts in maintaining stability, in response to Thursday morning's explosions in Urumqi.

Domestic security chief Meng Jianzhu vowed to "destroy the arrogance of violent terrorists", the statement said.

Public Security authorities have taken emergency measures, the statement added.

All the injured were rushed to several hospitals, police said.

Witnesses said two cross-country vehicles driving from north to south ploughed into people in the market at 7:50 am. Explosives were thrown out of the vehicles.

One of the vehicles exploded in the market.

A business runner in the market told Xinhua he heard a dozen of big bangs.

The open air morning market is located near the Renmin Park in downtown Urumqi. Ambulance and police cars are parking at the entrance of Park North Street leading to the market.

Flames and heavy smoke were seen. The scene has been cordoned off.