A Chinese government-backed agency has said Facebook and YouTube have refused to delete material involving terrorism and violence, which have become a major challenge, especially in the Xinjiang Uygur autonomous region.

In a campaign aimed at cracking down on online content with porn, scams, terrorism and violence, the China Internet Illegal Information Reporting Center received complaints about videos that promote jihad from the East Turkestan Islamic Movement - part of an international terrorism network listed by the United Nations Security Council - in the world's largest tech and social media websites including Facebook and YouTube.

Facebook and YouTube have made little effort to delete such information and hardly any content has been removed since its report of these gruesome videos, said the organization under the Internet Society of China.

Security analysts said China has seen a sharp rise in terrorist attacks, and files on the Internet are one of the causes.

Terrorist videos and audios released by ETIM spiked from 32 in 2012 to 109 in 2013, while attacks rose from two to seven over the same period.

Nearly all terrorists had watched or listened to videos and audio products before they carried out their atrocities, said Li Wei, an anti-terror specialist, when commenting on the latest multiple-explosion attack in Xinjiang on Sept 21.

Meanwhile, terrorists are using slick techniques to spread their content online.

In a report by the Guardian, the Islamic State's media arm even latched onto the huge interest in the Scottish independence referendum to distribute extremist material on Twitter and YouTube.

Wang Xin, an analyst from the Internet Society of China, said sophisticated strategies used by terrorist groups should prompt government departments to work even closer with social media companies.

However, since Facebook and YouTube have been blocked by China's firewall, improving their relationship with the Chinese government may not be easy.

Wang Xu contributed to this story.

Contact the writer at wangxu@chinadaily.com.cn