China will severely punish suspects responsible for a terrorist attack that left at least 29 civilians dead and over 140 injured in the southwestern city of Kunming, a spokesman told reporters on Sunday.

"This serious violent terrorist attack was planned and organized by separatist elements from Xinjiang and this incident was the most cruel atrocity," said Lü Xinhua, spokesman for the second session of the National Committee of the Chinese People's Political Consultative Conference.

"This ruthless indiscriminate killing of innocent people by violent and terrorist elements from Xinjiang fully exposed their anti-human and anti-social nature," he said.

The suspects will be punished to the full extent of the law, said Lyu a day ahead of the annual session of the country's top political advisory body.

More than 10 terrorist suspects attacked people at the square and ticket hall of the Kunming Railway Station at 9:20 p.m. Saturday.

Chinese President Xi Jinping has urged the law enforcement to investigate and solve the case of Kunming terrorist attack with all-out efforts and punish the terrorists in accordance with the law.

Violent terrorist attacks have been increasing since 2009 and have become the biggest security threat to Xinjiang.

Some 190 terrorist attacks were recorded in Xinjiang in 2012, increasing by a significant margin from 2011, according to the regional public security department.

Violence and terrorist activities have crossed the border of Xinjiang and the terrorists are aiming to cause bigger fear after an attack in Tian'anmen, an iconic place in the capital Beijing. Five people died and another 40 were injured after a car slammed into the Tian'anmen Square on Oct. 28 last year.