A group of religious extremists led by militants trained in overseas terrorist camps was behind the weekend attack on civilians in China's far-western Xinjiang Uygur Autonomous Region that left 6 dead and 15 others wounded, the local government said Monday.

The initial probe found that the group's leaders had learned how to make explosives and firearms in overseas camps of the terrorist group "East Turkistan Islamic Movement" (ETIM) in Pakistan before entering Xinjiang to organize terrorist activities, the government of Kashgar City said in an online statement.

Six civilians were killed, 15 others -- including three policemen -- were injured after attackers set fire to a restaurant and started randomly killing civilians in Kashgar on Sunday. Five suspects were shot dead by police.

The government on Monday also issued arrest warrants for two suspects who fled the scene. The two have been identified as 29-year-old Memtieli Tiliwaldi and 34-year-old Turson Hasan. Both are local ethnic Uygurs, according to the warrants.

The police have offered 100,000 yuan (15,384 U.S. dollars) for information which could lead to their arrests.

Pan Zhiping, a researcher with the Central Asia Studies Institute under the Xinjiang Academy of Social Sciences, called the ETIM "the most violent and dangerous" among the "East Turkistan" separatist forces. He said the organization is based somewhere along the Afghanistan-Pakistan border.

The ETIM traditionally trains its members for suicide bombings and car bombings before sending them to Xinjiang. But today more are using the Internet to penetrate the border to spread bomb-making techniques, Pan and other long-time Xinjiang observers said.

The United Nations and the Chinese government have labeled the ETIM an international terrorist organization.

The Sunday attack was the second violent case in Kashgar over the weekend. On Saturday night, two people hijacked a truck after killing the driver and drove it into crowded street. The suspects then jumped out of the truck and hacked bystanders randomly.

Eight civilians were killed while 27 others were injured. One of the suspects was killed in the clash while the other was apprehended.

The local government did not specifically label Saturday's attack as an act of terrorism.

Zhang Chunxian, secretary of Xinjiang regional committee of the Communist Party of China (CPC), has ordered a crackdown on terrorist attacks, religious extremist forces, and illegal religious activities at an emergency meeting held in the regional capital Urumqi following the attacks.

Zhang also ordered strengthened management of explosives.

He said the violent attacks would greatly damage the region's stability.

"People in Xinjiang should stay vigilant and recognize that terrorist attackers are the 'common enemies of all ethnic groups,'" Zhang said.

Xinjiang -- with 41.5 percent of its population Uygurs, a largely Muslim Chinese ethnic group -- is China's frontline against terrorism. The region borders eight central and western Asian countries, many of which have been attacked by terrorist and extremist militant groups.