Image copyright Reuters Image caption Hospitals in Kunming were inundated with the wounded

Chinese officials have blamed separatists from the north-western Xinjiang region for a mass knife attack at a railway station that left 29 people dead and at least 130 wounded.

A group of attackers, dressed in black, burst into the station in the south-west city of Kunming and began stabbing people at random.

Images from the scene posted online showed bodies lying in pools of blood.

State news agency Xinhua said police shot at least four suspects dead.

A female suspect was arrested and is being treated in hospital for unspecified injuries while a search continues for others who fled the scene, the BBC's Celia Hatton in Beijing reports.

Authorities described the incident as an "organised, premeditated, violent terrorist attack".

Image copyright AP Image caption There were scenes of shock and anguish after the attack

Image copyright AFP Image caption Evidence of the panic that ensued is scattered across the concourse

The Kunming city government later said that evidence from the scene pointed to separatists from Xinjiang as being behind the attack.

Analysis When news of the Kunming knife attacks surfaced on Chinese social media, many wondered whether Xinjiang separatists were responsible. Hours later, Kunming city authorities confirmed those suspicions, pointing to unnamed evidence found at the scene. One of the assailants was captured alive. According to Chinese state television, she will play a critical role in police efforts to piece together an episode that clearly caught them off guard. Witnesses say the "well trained" group easily overpowered security guards at the train station. In just 12 minutes, the knife-wielding attackers killed at least 29 people and injured 130 more. Once the majority group in Xinjiang, Uighurs now represent just 45% of the population. Many Uighur Muslims living in Xinjiang resent living under Chinese rule. They complain bitterly of the restrictions imposed on their religious practices. Only a small number appear to support the use of violence. But now, simmering anger inside the territory is spilling into other parts of China. In November, an SUV carrying three Uighurs intentionally crashed into a group of people standing near Tiananmen Square, killing five. Online, some in China are wondering how the government can possibly put an end to an ongoing cycle of security clampdowns in Xinjiang, followed by brutal attacks on unsuspecting Han Chinese.

It gave no details and the claim could not be verified.

Some of Xinjiang's minority Uighur Muslims want autonomy from Chinese rule and an end to state suppression of their religion.

Witnesses in Kunming said those who couldn't run quickly were cut down by the attackers' knives.

A survivor named Yang Haifei, who was wounded in the back and chest, told Xinhua he had been buying a train ticket when the attackers rushed into the station.

"I saw a person come straight at me with a long knife and I ran away with everyone," he said.

First reports said the attackers were only men, but witnesses and police later said the group also included women.

Chinese President Xi Jinping and Premier Li Keqiang sent condolences to the victims and their families.

President Xi urged "all-out efforts" to investigate the attack.

"Severely punish in accordance with the law the violent terrorists and resolutely crack down on those who have been swollen with arrogance," Xinhua quoted the president as saying.

The incident comes a few days before the opening of China's annual parliamentary session, the National People's Congress.

Our correspondent says domestic security is expected to top the agenda.

Last October China blamed Xinjiang separatists when a car was driven into a crowd of people on the edge of Beijing's Tiananamen Square, leaving five dead.