Police shot dead at least five of the alleged perpetrators at the train station in south-western Yunnan province, according to local television station K6.

Police officers sealed off a wide area around the station, and were questioning people at the site.

Ambulances took the victims to hospitals around the city.

One local hospital has reportedly declared a shortage of blood supplies.

Victims described attackers dressed in black bursting into Kunming railway station and slashing at people indiscriminately.

A victim named Yang Haifei, who was wounded in the chest and back, said he had been buying a train ticket when he saw a group of people, mostly wearing black, rush into the station and start attacking bystanders.

“I saw a person come straight at me with a long knife and I ran away with everyone,” he said, while others “simply fell on the ground”.

Some who had escaped were looking for missing loved ones.

“I can’t find my husband, and his phone went unanswered,” Yang Ziqing said.

She had been waiting for her train to Shanghai “when a knife-wielding man suddenly came at them”.

Photos posted on Chinese social media site Sino Weibo showed bloodstains across the station floor and medical staff attending to the injured, although the authenticity of the images could not be verified.

Weibo users took to the service to describe details of what happened, but many of those posts were quickly deleted by government censors, especially those that described the attackers, two of whom were identified by some as women.

Some reports suggested the women were wearing masks.

Others Weibo users condemned the attack.

“No matter who, for whatever reason, or of what race, chose somewhere so crowded as a train station, and made innocent people their target – they are evil and they should go to hell,” wrote one user.

China’s top security official Meng Jianzhu is reported to be travelling to Kunming in response to the attack, an indication of how seriously authorities view the events.

Yunnan has no history of terrorist attacks, and the motive for the stabbings was not immediately clear.

Authorities have not identified who they believe to have carried out the attack.

The attack comes ahead of China’s annual meeting of parliament, which opens in Beijing on Wednesday.

The party leadership is expected to lay out specific measures for economic reform.

The meeting is normally accompanied by a tightening of security across the country.

China has blamed similar incidents on Islamist extremists operating in the far western region of Xinjiang, though such attacks have generally been limited to Xinjiang itself.

Last month, police shot eight people in Xinjiang who they accused of planning to set off bombs made from gas cylinders.

China says its first major suicide attack, in Beijing’s Tiananmen Square in October, involved militants from Xinjiang, home to the Muslim Uighur people.

Many Uighurs believe China represses their traditional culture and customs.

Activists have accused China of importing Han Chinese, the majority ethnic group, into Uighur areas to reduce the minority group’s influence.

Uighurs make up around 46 per cent of Xinjiang’s 21.8 million residents, and many Uighurs say the Han Chinese influx has cost them land, jobs and business.

Hu Xijin, editor of the influential Global Times newspaper, published by the ruling Communist Party’s official People’s Daily, wrote on his Weibo account that the government should say who it suspected of the attack as soon as possible.

“If it was Xinjiang separatists, it needs to be announced promptly, as hearsay should not be allowed to fill the vacuum,” he said.

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

China suffered a spate of uncoordinated knife and cleaver attacks targeting schoolchildren in 2010.

At least 25 children were killed and over 100 injured in the attacks.

A number of measures, including a requirement to register with their national ID cards when buying knives, were introduced at the time.

Security guards were also posted in schools throughout the country.

The previous attacks were thought to be unrelated and blamed on the mentally ill rather than political terrorism.