Trials started Friday for four people accused of killing 31 people in a knife attack outside a railway station in the southern Chinese city of Kunming.

Kunming Intermediate People's Court said in a statement released Friday that Iskandar Ehet, Turgun Tohtunyaz and Hasayn Muhammad were standing trial on charges of organizing and leading a terror group and murder. The fourth person, Patigul Tohti, was being tried on charges of joining a terror group and murder.

The court said they were part of a terror group that plotted the March 1 attack, when five knife-wielding assailants hacked 31 people to death and injured another 141 people.

The attack shook the country amid escalating ethnic tensions between China's Muslim minority group of Uighurs and the majority Han people, which were once contained in the ethnic region of Xinjiang but began to spill to the rest of China late last year.

The court did not identify the suspects' ethnicity, but all have Uighur-sounding names.

Beijing has blamed religion-influenced terrorists with foreign ties for the Kunming attack and other violent incidents, which have left hundreds of people dead this year in and outside Xinjiang.

Critics say China's suppressive ethnic policies and practices as well as economic disenfranchisement have increasingly alienated the Uighurs, who may have been driven into religious extremism.

The Kunming court said the suspects, influenced by religious fundamentalism, had been plotting the attack since December.

Local authorities arrested Ehet, Tohtunyaz and Muhammad two days before the attack as they were attempting to illegally cross the border, the court said.

Having lost the contact with the three men, five other members of the group mounted the attack as planned, the court said.

Police shot dead four attackers and captured Tohti on the scene, the court said.

More than 300 people, including some victims and relatives of the suspects, were in attendance of the trials, the court said.