A mass stabbing at a Chinese train station late Saturday left 28 people dead and 113 injured in a "violent terrorist attack," state media said.
Victims described knife-wielding attackers dressed in black bursting into Kunming railway station and slashing indiscriminately.
Beijing's top security official was reported to be heading to the scene.
The incident which happened at around 9 p.m. (1 p.m. GMT) "was an organized, premeditated violent terrorist attack" carried out by "unidentified knife-wielding people," the official news agency Xinhua said, citing authorities.
Police shot dead five of the attackers at the train station in southwestern Yunnan province, Xinhua reported, and are "chasing the rest."
A knife victim named Yang Haifei, who was wounded in the chest and back, told Xinhua that he had been buying a train ticket when the attackers approached and had tried to escape with the crowd.
"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 desperately looking for missing loved ones.
"I can't find my husband, and his phone went unanswered," Yang Ziqing was quoted by Xinhua as saying.
She said she had been waiting for her train to Shanghai "when a knife-wielding man suddenly came at them."
Officers sealed off a wide area around the station, it added, while Xinhua said police were questioning people at the site.
The attackers were dressed in similar black clothing, the official China News Service said, citing eyewitnesses.
"A group of men carrying weapons burst into the train station plaza and the ticket hall, stabbing whoever they saw," it said.
State broadcaster CCTV called the incident a "terrorist attack" on its Weibo account.
China's top security official Meng Jianzhu would travel to Kunming to oversee its handling, CCTV said, while President Xi Jinping and Premier Li Keqiang sent condolences to the victims and their families.
Photos posted on Sina Weibo showed blood spattered across the station floor, and medical staff crouching over bodies lying on the ground, although the authenticity of the images could not be verified.
The photos showed crowds gathered outside among police officers and ambulances. The injured had been delivered to hospitals around the city, local television station K6 said.
A Weibo user going by the name HuangY3xin-Dione who was at a restaurant near the scene told how she saw a group of men in black with two long knives chasing people, Xinhua reported.
Another eyewitness told the Beijing News that she had seen two women in black walking towards the station and that some of the attackers had their faces covered.
Yunnan has no history of violent attacks, and the motive for the stabbings was not immediately clear, nor the identity or ethnicity of the perpetrators.
Knife and bomb attacks against local officials occur sporadically in China's far-western region of Xinjiang, where the mainly Muslim Uighur ethnic minority complain of cultural repression and tight security, while Beijing says it is facing a violent separatist movement.
Incidents involving Uighurs are often labelled "terrorist attacks" while others carried out by Chinese seen as having grievances against society or the authorities are not.
In a high-profile incident in Beijing last October, three Uighur family members set their car on fire at Tiananmen Square, the symbolic heart of the Chinese state, killing themselves and two bystanders.
The following month 41-year-old Feng Zhijun set off explosions outside a Communist Party office in the northern city of Taiyuan, killing one person and wounded eight.
Feng had previously served nine years in jail for theft and sought to "take revenge on society," Xinhua said.
In another prominent case last July, a wheelchair-bound man Ji Zhongxing set off a homemade bomb at Beijing's international airport in protest against alleged police brutality, but did not cause casualties.
Ji elicited widespread public sympathy and was sentenced to six months' jail.