The death toll of the May 22 terrorist attack in Urumqi has risen to 43, including four attackers, local police said on Saturday.

The central government launched on Friday a campaign to combat terrorism and violence in Xinjiang until June 2015, involving "extremely tough measures and extraordinary methods".

The Xinjiang Uygur autonomous region's government originally said on Thursday that 31 innocent people had been killed in the attack on a market in Xinjiang's capital.

DNA testing has identified the four attackers who drove two vehicles without license plates through roadside fences to indiscriminately run over shoppers at the open-air market on Gongyuanbei Street at 7:50 am.

Witnesses said the vehicles were driven at very high speeds as explosives were thrown and detonated among the crowd of about 5,000. Both vehicles then exploded, killing the four people inside.

Another suspect who allegedly helped plot the attack was caught later on Thursday in Xinjiang's Bayingolin Mongolian autonomous prefecture.

All five members of the terrorist cell formed at the end of 2013 are from Pishan county in southern Xinjiang's Hotan prefecture.

Police said the attacters — Nurahmat Ablipiz, Memet Memtimin, Raghimjan Memet, Memtimin Mahmat and Ablet Abdukadir — had long been influenced by religious extremism.

They took part in illegal religious activities, and watched and listened to violent terrorist video and audio materials.

Authorities have determined they purchased vehicles and materials for explosives, which they assembled, and then chose their target. Police are still investigating the attack.

At least 94 people were injured in the attack, most of whom were older than 50.

It is the most violent incident in the region since riots erupted in Urumqi on July 5, 2009, killing 197 people and injuring more than 1,700.

The regional government said it will combine the forces of legal authorities, the People's Liberation Army and armed police to bust terrorist cells and extremist religious groups. The joint force will also target workshops making guns and explosives as well as terrorist training camps.

The regional public security bureau, the high people's court and the people's procuratorate jointly issued a notice on Saturday, saying Xinjiang's legal bodies will harshly punish those involved in terrorist activities, including sponsoring terrorism, passing on such techniques as making explosives and illegally crossing the national border.

Security measures have been stepped up in Urumqi. All main shopping areas are guarded by armed police.

"There are obviously fewer people on the streets today," taxi driver Wang Zhiyong said, while passing a shopping mall.

"It will take a while for the city to recover this time because it's still pretty scary to think that they (the terrorists) have begun to target people like you and me."