BEIJING An Islamist militant group called the Turkistan Islamic Party (TIP) claimed responsibility for an attack at a train station in China's western city of Urumqi in late April that killed one and injured 79 people, the SITE Monitoring service said.
China had said the attack in its restive Xinjiang region, home to the Muslim Uighur ethnic group, was carried out by two religious extremists who were also killed in the blast.
Xinjiang, resource-rich and strategically located on the borders of central Asia, has been beset by violence for years, and a recent series of attacks, some of which Beijing has called terrorism, have unnerved the country.
SITE, which tracks Islamist militant statements, said TIP had released a 10-minute video in the Uighur language showing the construction of a briefcase bomb it said was used in the station attack.
"A fighter is shown placing the explosive material and shrapnel of bolts inside a box, then inserting the detonation device in a briefcase with the explosive, and leaving the trigger exposed in an outside pocket," SITE said of the video.
It said the video had been produced by the TIP's Islam Awazi Media Center and posted on its website on May 11.
Beijing says it faces a real threat from militant Islamists in Xinjiang who want an independent state called East Turkestan. Authorities say many have links with foreign groups, although rights groups and some foreign experts say there is little evidence to support this.
The TIP, which China equates with the East Turkestan Islamic Movement (ETIM), keeps a low profile in Pakistan. Unlike the Taliban, it rarely posts videos promoting its activities or ideology. Its exact size is unknown and some experts dispute its ability to orchestrate attacks in China, or that it exists at all as a cohesive group.
In a rare but brief interview with Reuters in March, Abdullah Mansour, who says he is the leader of the Turkistan Islamic Party, said it was his holy duty to fight the Chinese.
China's Foreign Ministry spokeswoman Hua Chunying said she had not seen the video, but that she believed it might further bolster China's position on separatist groups.
"Some violent extremist terrorist groups have now emerged. They are colluding with foreign groups and are attempting violent activities in Xinjiang and other areas in China intended to destroy China's national policy and social stability," Hua told a regular press briefing.
"We hope that everyone can recognize the goal of these violent groups and support the Chinese government's will to crack down on all violent terrorist activities and preserve safety for people and society," she said.
The TIP's claim comes as China tightens security in a number of cities after several recent deadly incidents in different parts of the country.
More than 100 people have been killed in unrest in Xinjiang in the past year. In March, 29 people were killed in an attack blamed on what Beijing described as knife-wielding terrorists from Xinjiang at a train station in the southwestern city of Kunming.
Exiled Uighur groups have repeatedly called for transparent investigations into the violence and say such incidents should not be used as excuses for further repressive policies on Uighur communities. Many Uighurs say they are unhappy at Chinese restrictions on their culture and religion, although the government says they are given widespread freedoms.
Last week, the government strengthened police patrols and restricted bulk purchases of gasoline in Beijing, where a car burst into flames on the edge of the Tiananmen Square in October, killing the three people in the car and two bystanders. China labeled it a suicide attack by Xinjiang militants.
China has sent weapons specialists to Xinjiang to train police how to better use guns as part of its crackdown, the ruling Communist Party's mouthpiece, the People's Daily, said.
The officers were sent to Xinjiang to "improve the anti-terrorism and emergency management ability of front-line police officers, and resolutely strike against violent terrorists who are swollen with arrogance," it said.
Police in the southwestern city of Guiyang have also recently been equipped with guns and ordered to patrol the city 24 hours a day, the official Xinhua news agency reported.
(Editing by Nick Macfie)