BEIJING (AFP) - Police in northeastern China on Monday killed three knife-wielding "terrorists" from Xinjiang, the mainly Muslim region in the far west, who attacked officers, local authorities said.

One other assailant described as a 28-year-old woman was injured in Liaoning, said a notice posted on a verified provincial government social media account.

Shenyang, the Liaoning capital where the incident happened, is almost 3,000 km from Urumqi, the capital of Xinjiang, which has seen sporadic violence in recent years blamed by authorities on Islamist terrorists.

The restive region is home to most of China's 10 million Uighurs, a Turkic-speaking Muslim minority, who rights groups say face religious and cultural discrimination.

Fatal incidents outside Xinjiang, but linked to the violence in the region, are rare.

In March 2014, 31 people were knifed to death by "Xinjiang separatists" in a mass stabbing at a train station in Kunming in the southwest, with four attackers killed.

That came after, according to authorities, three people from a Xinjiang family crashed their car into crowds in Tiananmen Square, the symbolic heart of the Chinese state, killing themselves and two visitors, raising the spectre of spreading violence.

All four alleged attackers in Shenyang were described as "Xinjiang terrorists", with the woman, whose name was given phonetically as Amanguli Maititusong, identified as a Uighur.

There were no other injuries, casualties or "effects on society", said a police notice on the province's official Sina Weibo, a Twitter-like website. Three children who were with the attackers were removed by police, it added.

Clashes between authorities and alleged Islamist separatists - as well as attacks killing civilians - have spread in recent years, both in Xinjiang and outside it.

Rights groups say Uighurs suffer from religious repression and discrimination. Authorities have tightly restricted independent reporting on these incidents in the past.

Beijing launched a "strike hard" campaign in the province just over a year ago after an attack on a train station in Urumqi as Chinese President Xi Jinping was visiting the city.

Police had been conducting a drive against "terrorism" in Shenyang since June 12 and had already arrested 16 people by Monday when police visited the house where the four people were living, the notice said.

The four adults attacked police with knives and blunt objects while "shouting jihadist slogans", according to the police. Photos posted on Sina Weibo showed security forces on rooftops with rifles and a man being carried through the streets on a stretcher.

Others showed another man with a deep gash in his cheek and blood on the ground. The veracity of the photos could not be independently confirmed by AFP.

More than 200 people died last year in violence either in or traced back to Xinjiang, according to media reports. But the vast majority of incidents are confined to Xinjiang itself.