Anti-terrorism experts said the crackdown on terrorist-linked video and audio content on the Internet must intensify, as such information has fueled the spread of religious extremism and terrorist attacks in China.

Video and audio files released on the Internet by the East Turkistan Islamic Movement have spiked - from 32 files in 2012 to 109 last year. In the first three months of this year, the terrorist group released 36 such files.

Terrorist attacks in China also rose sharply last year, and the video and audio files are a direct cause of the increase, security analysts said.

On June 26, 16 terrorists launched an attack in Lukqun, a township in Turpan prefecture of the Xinjiang Uygur autonomous region, leaving 35 dead.

The principal criminal of the gang, Ekrem Usman, said: "We watched some videos, which told us to launch jihad (holy war). We started to watch those videos in 2013."

"He (Ekrem Usman) downloaded the video made by the East Turkistan Islamic Movement, which advocates jihad, to his cellphone at home, then drew people to join his group. He played the video and audio files when they held meetings and gradually developed their ideas of religious extremism," said an officer from the Piquan county public security bureau in Xinjiang.

Terrorists from Xinjiang drove a jeep into a crowd at Tian'anmen Square in Beijing and set the vehicle on fire on Oct 28. Five people, including the three in the jeep, died, and 40 others were injured.

One of the suspects, Yusanjan Wuxuer, who participated in planning the attack, said: "Except for reading books and watching videos, I also received some materials from Usman Asan (the terrorist who killed himself in the attack). Nobody else spread the 'ideas' (extremist and terrorist ideology) to me."

After an attack in Xinjiang's capital, Urumqi, on April 30, which killed three and injured 79 others, the ETIM released a video on how to make a briefcase bomb of the type that was used in the attack. It also claimed responsibility for it.

The "Turkestan Islamic Party", the other name of the ETIM, released a video on the Internet referring to the Tian'anmen attack as "jihad".

After the June 26 terrorist attack in Lukqun, the group released a statement: "It's Allah's order and the act of worship we must do to attack Chinese government organs and police stations and kill heretics and Muslims working for the Chinese government."

According to Xinjiang police, several terrorist attacks against government organs occurred after the statement was released.

With the help of their own or other terrorist groups' websites, free online storage facilities, file-sharing portals, social networking platforms and e-books, the ETIM promotes itself and spreads extremism via videos, said Yalikun Yakuf, deputy director-general of the Xinjiang public security department.

"The terrorists in China recruit new members by downloading those videos made by the ETIM and organize people to watch them, then launch terrorist activities," he said.

"All those who participated in the terrorist attacks of ETIM have watched the videos, produced at home or abroad, that advocate terrorism, separatism or jihad," said Li Sheng, a professor at the Xinjiang development research center of the Chinese Academy of Social Sciences.

Apart from strengthening related legislation to prevent the spread of the video and audio content that fuels extremist ideology and instigates ethnic conflict, the government should also promote knowledge of the laws governing such criminal behavior among the public, Li said.

"Even as we protect the Internet and citizens' freedom of speech, we shouldn't give opportunities to the terrorists to make use of that freedom to spread their terrorist ideas," said Li Wei, an anti-terrorism researcher at the China Institutes of Contemporary International Relations.

The ETIM, which advocates violence to force the separation of Xinjiang from China, has been identified as a terrorist group by China, the United States, the European Union and the United Nations.