A "strike hard" campaign against what China calls terrorism in the largely Muslim region of Xinjiang and beyond has seen 181 gangs busted, authorities said Monday, a year after the controversial measures were launched.

Rights groups have labelled the crackdown discriminatory, raising further concerns after Beijing announced in January the measures would be extended until at least the end of 2015.

Authorities launched the campaign after 39 people were killed last May in a bloody market attack which was blamed on separatists in Urumqi, the capital of the vast, north-western region of Xinjiang.

Scores of people have been sentenced to death as part of the drive, while hundreds have been jailed or detained on terror-related offences.

"As of April 30 this year, 181 violent terror gangs have been destroyed, with 96.2 percent being thwarted at the planning phase," the Xinjiang government's Tianshan web portal reported, adding that 112 suspects surrendered to the police.

Clashes between authorities and alleged Islamist separatists -- as well as attacks killing civilians -- have spread in recent years, both in Xinjiang, which is home to just over 10 million of the mainly Muslim Uighur minority, and outside it.

More than 200 people died last year in violence either in or traced back to Xinjiang, according to media reports.

Among the most shocking incidents was a deadly rampage by knife-wielding assailants at a train station at Kunming in China's southwest, when 31 people were killed and four attackers died.

Three men convicted on terror charges were executed this March for their part in the attack.

Authorities have also targeted religious practices, such as the wearing of veils, which activists say has created an atmosphere of repression and led to violence.

China defends its policies, arguing that it has boosted economic development in the area and that it upholds minority and religious rights in a country with 56 recognised ethnic groups.

But Dilxat Raxit, spokesman for the Munich-based World Uyghur Congress, said: "So-called equal laws deprive Uighurs of freedom of expression and rights.

"The law upholds Beijing's political interests rather than judicial justice, and it is possible for any person at any time... to lose their freedom for being resentful of China's policies," he said in an emailed statement.