Explosion in China's Xinjiang Kills 31

Police vehicles of the Special Weapons and Tactics (SWAT) team are seen after a blast occurred, on a road in Urumqi, Xinjiang Uighur Autonomous Region, May 22, 2014.
Chinese state media say a bomb attack has killed 31 people at a busy market in the capital of the ethnically divided Xinjiang region.

The official Xinhua news agency says more than 90 people were injured when two cross-country vehicles crashed into a group of people in downtown Urumqi, near Renmin Park.

Witnesses say explosives were then thrown out of the vehicles and that as many as a dozen "big bangs" were heard. Xinhua said one of the vehicles exploded.

Another state-run media outlet, the People's Daily, said officials have determined the incident is a terrorist attack and that the Chief of National Public Security is headed to Urumqi.

Xinhua says Chinese President Xi Jinping has pledged to "severely punish terrorists" following the incident.

Foreign Ministry spokesman Hong Lei called the attackers "anti-human," stressing that Beijing is "confident and capable of cracking down on violent terrorists." No one has claimed responsibility for the attack.

"The Chinese government has the confidence and the ability to combat the terrorists. These terrorists are swollen with arrogance. Their schemes will not succeed," said Hong Lei.

Pictures posted on social media showed fire and large plumes of black smoke rising from the scene. Some victims were being carried away, while others were lying in the street.

China's Ministry of Public Security called the blast a “serious violent terrorist incident.”

There were major casualties in the blast, the ministry said in a statement on Thursday. Domestic security chief Meng Jianzhu vowed to “destroy the arrogance of violent terrorists,” the statement read.

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

It is the latest attack to hit Xinjiang, which is home to the mainly Muslim Uighur minority group. China blames violence in the region on foreign-backed Muslim separatists.

Last month, one person was killed and dozens injured by assailants armed with knives and explosives at an Urumqi train station. Both attackers died.

Exiled Uighur groups say the attacks are driven by the heavy-handed restrictions on Uighur religious life and by policies that favor the majority Han ethnic group.

It is difficult to verify information about the attacks because China severely restricts journalists from operating in Xinjiang and surrounding areas.

China has been waging an offensive on what it calls the three evils of terrorism, separatism and extremism in Xinjiang and the neighboring region of Tibet.

Thursday's attack in Urumqi comes a day after China jailed 39 people in Xinjiang after finding them guilty of offenses including spreading videos that incite terrorism.

Some information in this report was contributed by Reuters.