A mass stabbing at a Chinese train station late Saturday which left 27 people dead and 109 injured was 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 "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 a number of the perpetrators at the train station in southwestern Yunnan province, according to posts by local television station K6 on its official Sina Weibo account, the Chinese equivalent of Twitter.
Officers sealed off a wide area around the station, it added, while Xinhua said they were still questioning people at the site.
Meanwhile ambulances had delivered the injured to hospitals around the city, K6 reported.
The attackers carried knives and 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.
Photos posted on Sina Weibo showed blood spattered across the floor and medical staff crouching over bodies lying on the ground, although the authenticity of the images could not be verified.
Crowds gathered outside the station among police officers and ambulances, the images also showed.
State broadcaster CCTV also called the incident a "terrorist attack" on its Weibo account.
China's top security official Meng Jianzhu would travel to Kunming, it said, while President Xi Jinping and Premier Li Keqiang sent condolences to the victims and their families.
Yunnan has no history of violent attacks, and the motive for the stabbings was not immediately clear.