Chinese state-run media on Wednesday played up a visit to the violence-prone far western region of Xinjiang by President Xi Jinping, who encouraged tougher law enforcement and stepped-up assimilation of minorities.

The vast and nominally autonomous region, where mostly Muslim Uighurs are the largest ethnic group, is periodically hit by deadly clashes that authorities blame on terrorists but which rights groups say are driven by cultural repression.

Xi urged on law enforcement personnel in Kashgar, in his first visit to Xinjiang since becoming head of China's ruling Communist Party in November 2012.

"It is necessary that you have effective methods to handle violent and terrorist criminals," Xi said, the state-run China Daily newspaper reported, citing the official Xinhua news agency.

"The training must simulate real combat," Xi added. "Sweat more in peacetime to bleed less in wartime."

On its front page the paper carried a photo of Xi grinning as he visited a Kashgar home, holding the hand and wrist of family members seated with him on a sofa, traditional foods set out on a table before them.

But he called the area the "front line" in terms of fighting terrorism and maintaining social stability.

"The situation is grim and complicated," he said.

Xi's "inspection tour" to Xinjiang follows his chairing of the first meeting of China's new national security commission two weeks ago.

"China now faces the most complicated internal and external factors in history," Xinhua paraphrased him as saying then.

Ethnic rioting in the Xinjiang capital Urumqi in 2009 left around 200 people dead and resulted in a security crackdown, but more recently violence has spread beyond the region.

A machete attack on passengers and passers-by at a railway station in the southern province of Yunnan in March killed 29 people and wounded 143.

Authorities blame the violence on separatists with ties to foreign terrorist groups, though rights groups and experts say the threat is exaggerated to justify religious and cultural restrictions and is amplified by decades of migration to the region by members of China's Han majority.

Xi also visited a primary school, where he called on teachers to make students bilingual.

"Learning Mandarin will not only make it easier for these children to find jobs in the future, but more important, it can contribute to promoting ethnic unity," Xi said, according to the China Daily.

He also took the opportunity to encourage Han teachers to learn the Uighur language, it added.

An editorial in the Chinese-language edition of the Global Times newspaper used Xi's trip to call for people elsewhere in China to be unafraid and venture to Xinjiang "to travel and hold meetings and be resolutely determined to sweep away the odour of terror hurled at society by terrorist elements".

Such groups were working to bring about "ethnic estrangement" and isolate Xinjiang from Chinese society, it said.

"We cannot let this malicious goal of theirs prevail."