Explosions at an open-air market in Urumqi, capital of Northwest China's Xinjiang Uygur autonomous region, on Thursday morning, have left 31 people dead and more than 90 others injured.

China's Ministry of Public Security called the blasts "a serious violent terrorist incident", and a witness who was buying groceries at the market said he saw vehicles plough into people and also explosives thrown out of the vehicles.

"I heard a series of large explosions and the vehicles were soon on fire, with flames rising so high they could reach the second floor of a building," the witness said.

Another witness, a man surnamed Wang, cried as he described the scene. "I started to run as soon as I heard the explosions and one blast was quite close to me," Wang said, adding he has never felt so scared in all his life.

Related: Live: 31 dead, 94 injured in Urumqi terrorist bombing