Updated version with much more information:

28 Dead, 113 Injured in Train Station Knife Attack
BEIJING March 1, 2014 (AP)

[....] authorities considered it to be "an organized, premeditated violent terrorist attack."[....]

In an indication of how seriously authorities viewed the attack, one of China's deadliest in recent years, the country's top police official, Politburo member Meng Jianzhu, was on route to Kunming, the Communist Party-run People's Daily reported.

The violence in Kunming came at a sensitive time as political leaders in Beijing prepared for Wednesday's opening of the annual meeting of the nominal legislature where the government of President Xi Jinping will deliver its first one-year work report.

A Xinhua reporter on the scene in Kunming said several suspects had been "controlled" while police continued their investigation of people at the station. The reporter said firefighters and emergency medical personnel were at the station and rushing injured people to hospitals for treatment.

The authorities said five suspects were shot dead but that their identities had not yet been confirmed, Xinhua reported. [.....]

Yang Haifei, a Yunnan province resident who was being treated at the hospital for wounds to his chest and back, told Xinhua that he was buying a ticket when he saw a group of people, most of them dressed in black, rush into the station and start attacking people.

"I saw a person come straight at me with a long knife and I ran away with everyone," he told Xinhua, adding that people who were slower ended up severely injured. "They just fell on the ground," Yang said.

At the guard pavilion in front of the station, three victims were crying [....]

Use of knife attacks by Uighur separatists is not a new thing, if that indeed is what they are dealing with here.  Two previous examples are in this timeline offered by the South China Morning Post at the end of this report. There was also "wave of syringe stabbings" (government saying 500 victims!) and there have been bombings including suicide bombings, a hostage situation (weapon unknown) and even one case of "gunfights":

Chronology of key events related to the restive region since 2009:

2009

June 25 Two Uighur factory workers are reported killed and dozens injured in a huge brawl with Han Chinese in Shaoguan, in the southern province of Guangdong.

July 5 Hundreds, perhaps thousands, of Uighurs riot in the Xinjiang capital Urumqi after security forces move in on a protest over the Shaoguan incident.

July 7 The government says nearly 200 people died in the unrest, with more than 1,600 injured and hundreds arrested. Eventually at least 26 are reportedly sentenced to death.

September 2 -- Han residents of Urumqi protest for days over a wave of syringe stabbings which the government eventually says had nearly 500 victims, blaming “ethnic separatist forces”.

2011

July 18 Police kill 20 protesters in clashes in Hotan, southern Xinjiang, exiled Uighur groups say. State media say police fired on demonstrators who attacked a police station, killing one officer.

July 31-August 1 Two attacks by alleged terrorists leave 13 people dead in a Han Chinese section of Kashgar, while police kill eight suspected Uighur separatists.

September 15 Courts in Xinjiang sentence to death four Uighurs over the July incidents.

December 28 Police in Pishan kill seven “terrorists” in a hostage standoff that left one officer dead. State media calls them terrorists engaged in a “holy war”.

2012

February 28 Rioters armed with knives kill at least 10 people in Yecheng, while police shoot two of the attackers dead, state press say. One man is later sentenced to death.

2013

April 23 Gunfights in Bachu leave 15 police and community workers and six “terrorists” dead. Two men are later sentenced to death.

June 26 At least 35 people are killed when, according to Xinhua, “knife-wielding mobs” attack police stations and other sites in Lukqun before security personnel open fire. Three people are later sentenced to death.

August 20 A Chinese policeman is killed in what state media call an “anti-terrorism” operation in Yilkiqi. Overseas media report 22 Uighurs were shot dead.

October 28 Three members of the same Xinjiang family crash their car into tourists in Tiananmen Square in Beijing, the symbolic heart of the Chinese state, killing two, before setting it on fire and dying themselves, according to authorities who call it a terrorist attack.

November 17 Two policemen and nine attackers are killed at a police station in Serikbuya, state media say. Rights groups say the trigger was the fatal shooting of a Uighur youth during a protest.

December 16 14 Uighurs and two police officers are killed in Shufu county. Authorities describe the slain Uighurs as members of an extremist group, but campaigners say police raided a house where a family was preparing for a wedding, with six women among those killed.

December 30 An assault on a police station in Yarkand leaves eight attackers dead, according to the Xinjiang government’s official website.

2014

January 15 A prominent Uighur academic and critic of government policy, economics lecturer Ilham Tohti, is detained by police, his wife says, and later charged with separatism, which can carry the death penalty.

January 25 A total of 12 people have been killed in Xinhe, six in explosions and six shot dead by police dealing with “violent incidents”, a government-run news portal says.

February 14 A total of 11 people die in an attack on police in Wushi, with officers shooting eight dead and three blowing themselves up, authorities say.

March 1 At least 29 people are killed and more than 130 wounded by knife-wielding assailants at Kunming train station in Yunnan province, more than 1,600 kilometres from Xinjiang. Officials blame separatist terrorists from Xinjiang.

Note he is reporting from Kunming ( & also that he presents the government's narrative as wanting to promote the idea that ethnic groups are living in harmony, by downplaying the Uighur I.D., but playing up that these were "terrorists" ):

Attack Strains Already Tense Relations Between China’s Han and Uighurs
By Andrew Jacobs, New York Times, March 3/4, 2014

KUNMING, China — Even with the objects of his ire in earshot, the landlord barely lowered his voice to describe his Uighur neighbors, who also happened to be his tenants.

“During the day they look like human beings, but at night they are thieves and thugs,” he said as a group of elderly women in traditional head scarves drank tea in the courtyard of his building. “Even the police are afraid of them. We all hate them, but there’s nothing to be done about it.”

It is fair to say that relations have never been easy between the ethnic Han who dominate this vast nation and the Uighur minority whose traditional homeland is in China’s far western borderlands. But in the two days since a group of assailants rampaged through the Kunming Railway Station here in southwestern China, killing at least 29 people and wounding 143, the official narrative of a kaleidoscope of ethnic groups living in harmony is being tested by the news that the killers were from the Xinjiang Uighur Autonomous Region [.....]

From the author who wrote the "Letter from China" column @ The New Yorker for years:

After 3/1: The Dangers of China’s Ethnic Divide
By Evan Osnos, News Desk @ newyorker.com, March 3, 2014

Violence as savage and public as the massacre that took place at a Chinese train station on Saturday shocks the chemistry of a country in a way that years of more remote, simmering conflict do not. Acts of such spectacular violence exert unpredictable forces on the public and on the leaders who are charged with protecting it, transforming judgments of when and how to use force and decisions about what can be sacrificed in the name of security, as well as the definitions of citizenship, patriotism, and innocence. Rarely do they leave anyone better off than they were before.

When eight assailants armed with foot-long sabers set upon men and women in the southwestern city of Kunming, killing at least twenty-nine people and injuring a hundred and forty-three, they struck in a place and a manner that nobody in China had anticipated. For all its epic history of bloodshed, the People’s Republic is unaccustomed to this kind of threat against citizens going about their daily lives, and, by day’s end, the attack was seared into public consciousness in a way that, since 9/11, has become customary for these moments around the world: it is the 3/1 incident. A message in wide circulation declared, “We are all Kunmingers.”

Chinese authorities say the attack was “orchestrated by Xinjiang separatists [....]