URUMQI: Mobs wielding makeshift weapons roamed this restive city Wednesday, with vigilantes pummelling two Uighur Muslims, despite a massive show of force by Chinese troops that brought some calm.

President Hu Jintao abandoned a Group of Eight summit in Italy, in what observers said was an unprecedented move, to tackle one of China's worst spikes in ethnic tensions in decades.

In Urumqi, the capital of the remote northwest Xinjiang region where 156 people died in unrest on Sunday, army helicopters circled overhead as thousands of soldiers and riot police filled the city shouting out "protect the people".

"We support this," said a 45-year-old Han Chinese as he watched the troops roll by in trucks.

"But they should have got here sooner. It took them three days to do this. Why so long?"

After authorities blamed Muslim Uighurs for Sunday's unrest that also left more than 1,000 people injured, Han Chinese took to the streets Tuesday with shovels, meat cleavers and other makeshift weapons vowing to defend themselves.

After a night-time curfew was declared on Tuesday, Chinese authorities appeared determined to show they were able to maintain order.

Thousands of riot police wearing helmets and carrying shields lined up on a main road in Urumqi dividing the city centre from a Uighur district, with columns of soldiers behind them.

The security build-up had an impact with fewer people wielding makeshift weapons taking to the streets, and Urumqi mayor Jerla Isamudin told reporters in the late afternoon that the situation in the city was "under control".

He also warned that anyone found guilty of murder in connection to the unrest would be given the death penalty.

But tensions remained high, with some Han Chinese and Uighurs continuing to arm themselves with sticks, poles, knives and other weapons, leading to confrontations and violence, according to AFP reporters.

In one of two attacks witnessed by AFP reporters, about 20 Han Chinese men armed with wooden bats attacked a Uighur man in central Urumqi.

The beating stopped after about one minute when security forces moved in to disperse the mob, the AFP reporter said, while a local Han Chinese woman said the victim was a Uighur man.

The extent of the man's injuries was unclear, as he was quickly taken away.

In the second incident, a group of Han Chinese saw three Uighurs at an intersection and chased them.

Two of the Uighurs escaped, but a third was caught by some of the crowd and he was assaulted for around 30 seconds, before police took him away. AFP reporters said he had blood on his face after the beating.

In another incident, about 200 Uighurs armed with sticks, pipes and rocks began protesting directly in front of a police cordon that was dividing their neighbourhood from a Han-populated area, an AFP reporter witnessed.

The crowd of Uighurs grew after a helicopter dropped leaflets blaming Sunday's unrest on exiled Uighur leader Rebiya Kadeer, but they also claimed police had overnight allowed Han Chinese to freely attack Muslim areas.

In a BBC interview on Wednesday, Kadeer blamed Chinese policies for the violent unrest and claimed the death toll from riots was "much higher" than the 156 stated by Beijing.

Official news agency Xinhua late Wednesday reported government sources as saying they had evidence the riot was "instigated and masterminded" by Kadeer, citing "recordings of calls" which referred to unrest ahead of the rioting.

China's state media said Wednesday over 100 people "killed by rioters" in the initial violence had been identified, providing the first partial breakdown of the death toll.

Highlighting the severity of the crisis, the government announced Hu had cut short his trip to Italy for the G8 summit.

"I have never seen a Chinese president shorten a trip abroad before... there is clear concern," said Jean-Pierre Cabestan, professor of political science at Hong Kong Baptist University.

Xinjiang's eight million Uighurs make up nearly half the population of the region, a vast area of deserts and mountains rich in natural resources that borders Central Asia.

The Turkic-speaking people have long complained of repression and discrimination under Chinese rule, but Beijing insists it has brought economic prosperity to the region.