An attack by knife-wielding men at a railway station in Kunming in south-west China has left at least 29 dead, the state news agency Xinhua says.
Another 130 people were wounded in what authorities said was a "premeditated, violent terrorist attack".
Four suspects were shot dead, one arrested and other are being sought Xinhua said.
City officials said evidence implicated militants from the western region of Xinjiang, but this was not verified.
President Xi Jinping and Premier Li Keqiang have 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.
Pools of blood
Witnesses said that the men, who were mostly dressed in black, attacked people at random.
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.
He added that those too slow to flee were cut down.
Some who escaped were desperately looking for missing loved ones.
Yang Ziqing told Xinhua she and her husband had been waiting for a train to Shanghai "when a knife-wielding man suddenly came at them".
"I can't find my husband, and his phone went unanswered," she said.
Social media users in China posted pictures of the attack on the internet, but correspondents say they are being taken down.
Images seen by the BBC show men and women lying on the floor in pools of blood following the attack.
Kunming officials, quoted by Xinhua, later said that evidence at the scene showed it was "a terrorist attack carried out by Xinjiang separatist forces".
Xinjiang is home to the Muslim Uighur minority group which has a long history of discord with Chinese authorities.
State broadcaster CCTV said top security official Meng Jianzhu would travel to Kunming to oversee the handling of the investigation.