Chinese police blamed the East Turkestan Islamic Movement (ETIM) for a train station attack in the western city of Urumqi last month that killed three people, Xinhua said on Sunday, the first time the separatists have been directly linked to the assault.
The brief report carried by China's state news agency did not give more details. Seventy-nine people were also injured in the attack in late April.
Until now China had said the attack in its troubled Xinjiang region, home to the Muslim Uighur ethnic group, was carried out by two religious extremists who were also killed in the blast.
State media had said "knife-wielding mobs slashed people" at an exit of the South Railway Station of Urumqi, capital of Xinjiang, and set off explosives.
Chinese police have arrested seven people suspected of involvement in the attack, the state-backed newspaper Global Times reported on Saturday.
Many Uighurs call Xinjiang East Turkestan. China's government often blames the frequent outbreaks of violence there on extremists agitating for an independent state.
An Islamist militant group called the Turkistan Islamic Party (TIP), which China equates with the ETIM, claimed responsibility for the attack, the SITE Monitoring service, which tracks Islamist militants, has said.
The United Nations and Washington placed the ETIM on lists of terrorist organisations after the September 11, 2001, attacks in the United States.
The ETIM has been accused by the United States and China of having ties to al Qaeda but there is disagreement among security experts over the nature of the group and whether ties with al Qaeda and other militant organisations really exist.
Rights organisations have said there is little concrete evidence that the group has carried out most of the attacks for which it has been blamed and that Beijing uses the ETIM as an excuse to push repressive policies on Uighurs.
Last year, China's domestic security chief said he believed a vehicle crash in Beijing's Tiananmen Square in which five people died was planned by the ETIM.
Xinjiang has been beset by violence for years and recent attacks, some of which Beijing has called terrorism, have unnerved the country. More than 100 people have been killed in unrest in Xinjiang in the past year.
The government has often blamed ETIM for some of these incidents, even though many experts and rights groups have cast doubt on its existence as a cohesive group.
Many rights groups say China has long overplayed the threat posed to justify its tough controls in energy-rich Xinjiang, which is strategically placed on the borders of Central Asia, India and Pakistan.
Many of Xinjiang's Turkic-speaking, Muslim people chafe at restrictions on their culture, language and religion, although the government insists it grants them broad freedoms.