A local court in Turpan, Northwest China's Xinjiang Uyghur Autonomous Region, on Thursday sentenced three convicts to death and one person to 25 years in jail for a violent terrorist attack in Shanshan county on June 26.

The verdicts, handed down by the Turpan Prefectural Intermediate People's Court, were given to the four convicts on charges of leading terrorist organizations, murder and arson.

The four, including a man named Ahmatniyaz Sidiq, were accused of playing a principal role in a deadly attack against a local government building and police station in the township of Lukqun, in which 24 people, including 16 Uyghurs and two police officers, were killed and another 23 injured.

Local police shot dead 11 attackers and apprehended four at the scene. Economic losses of 2.14 million yuan ($349,787) were also reported as a result of the riot.

The court said the four convicts, including Sadiq, had been illegally conducting religious activities, propagating extremist religious thought, listening to audio material that incites violent terrorist activities and receiving physical training to conduct terrorist attacks in Lukqun township in the county since April 2010. 

Local authorities said earlier that Sadiq formed a terrorist group with 17 members. Since mid-June, the group raised some 10,800 yuan, and on June 19, key leaders of the group orchestrated attacks on the police station, government office, armed police station and market.

Days before their attack, they bought tools including 26 machetes, 21 knives and gasoline, the local news portal Tianshan Net reported.

The attack was launched ahead of schedule, after a group member was detained when he was sharpening the knives to be used in the riot.

Authorities have on many occasions warned against the three forces of terrorism, religious extremism and separatism, both domestic and abroad. A number of fatal terrorist attacks have taken place in Xinjiang in the past few years.

"Law enforcement personnel have become their main target, and instead of launching suicide attacks, they focus on training and recruiting new members and promoting their values," Li Wei, an expert on anti-terrorism with the Chinese Institutes of Contemporary International Relations, said in an earlier interview.

Xinhua contributed to this story