Chinese police have captured three suspects for a knife-wielding railway station attack that killed 29 people and wounded 143, authorities told state media.

"Three suspects involved in the terrorist attack in the southwestern city of Kunming had been captured," the official news agency Xinhua said on Monday, citing the Ministry of Public Security.

Altogether eight members of a "terrorist gang" carried out the stabbing spree late on Saturday, Xinhua said.

Four more of the group were shot dead by police and a wounded woman was captured at the scene, it continued, naming their leader as Abdurehim Kurban.

China has blamed separatists from its restive far-western region of Xinjiang, home to the mainly Muslim Uighur minority, for what it describes as an "act of terror", with state media dubbing the incident "China's 9/11".

The incident that happened at around 9pm local time (1pm GMT) on Saturday night at Kunming Railway Station in Yunnan province "was an organised, premeditated violent terrorist attack", Xinhua earlier reported, citing authorities.

Defiant Kunming residents queued to donate blood on Monday while others vented their anger.

Many Chinese Internet users accused the US of double standards on social media, after Washington condemned the bloody rampage by attackers but refrained from calling it a terrorist incident.

Xinjiang fighters blamed

Meng Jianzhu, China's top security official, arrived in Kunming early on Monday to oversee the handling of the incident, while President Xi Jinping and Premier Li Keqiang sent condolences to the victims and their families.

Meng visited the injured and their families and then went to the Kunming Railway Station to investigate the scene.

China has seen a number of mass stabbings and other attacks in recent times carried out by people bearing grudges against society.

Beijing has blamed similar incidents in the past on fighters operating in Xinjiang. Such attacks have generally been limited to Xinjiang itself.

The attack comes at a sensitive time as China gears up for the annual meeting of parliament, which opens in Beijing on Wednesday and is normally accompanied by a tightening of security across the country.