The Turkistan Islamic Party (TIP), a terrorist group with members mainly from Northwest China's Xinjiang Uyghur Autonomous Region, claimed responsibility for an attack at a train station in Urumqi in late April, SITE monitoring service said.

SITE, which tracks Islamist militant statements, said TIP released a 10-minute video in the Uyghur language showing the construction of a briefcase bomb it said was used in the station attack.

The attack on April 30, which was carried out by two terrorists, killed one and injured 79. Both attackers also died in the blast.

"A fighter is shown placing the explosive material and shrapnel 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 TIP's Islam Awazi Media Center and posted on its website on Sunday.

TIP was formerly known as the East Turkestan Islamic Movement (ETIM), a group responsible for multiple terrorist attacks inside and outside of Xinjiang. 

"There are two things worth noticing this time. One, more often than before, the terrorists call themselves TIP rather than ETIM, which is a signal that they want to emphasize their region and their future tendency. It indicates that more separatists from Xinjiang are gathered under the name and more terrorists from the Afghan-Pakistan border as well as other regions are traveling to Turkey to join the organization," a source familiar with the organization, told the Global Times.

"Two, it is rare that the group revealed the procedure of bomb making, which shows its terrorist nature in front of the world. Media outlets in the West who often labeled the group 'Islamic militants' should now be very clear of its terrorist nature," said the source.

In a rare but brief interview with Reuters in March, Abdullah Mansour, who says he is the leader of TIP, said it was his holy duty to fight the Chinese.

"From another point of view, the open declaration of responsibility is a sign that the group is in eager pursuit of support and recognition from other terrorist organizations in the world. However, its capability to make explosives is a warning to Chinese police that their counter-terrorism measures must be improved accordingly," the source noted.

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 Wednesday.

"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.

Reuters contributed to this story