Banks of paramilitary police fanned out in the far-flung Chinese city of Urumqi on Wednesday to try to stifle unrest days after 156 people were killed in the region's worst ethnic violence in decades.

A Communist Party official vowed to execute those guilty of murder in the riots. 

Urumqi, capital of the northwestern region of Xinjiang, imposed an overnight curfew on Tuesday after thousands of Han Chinese, armed with sticks, knives and metal bars, stormed through its streets demanding redress and sometimes extracting bloody vengeance on Muslim Uighurs for Sunday's violence.

Many took to the streets again on Wednesday and even with helicopters hovering overhead there were scuffles in a volatile crowd of around 1,000 as police seized apparent ringleaders, prompting cries of "release them, release them."

President Hu Jintao abandoned plans to attend a G8 summit in Italy, returning home to monitor developments in energy-rich Xinjiang, where 1,080 people were also wounded in rioting and 1,434 have been arrested since Sunday.

Financial markets again appeared unaffected and life was returning to the streets of Uighur neighborhoods. But residents said night-time arrests were continuing and they were quietly preparing to defend against further Han attacks.

Urumqi airport was crowded with people anxious to leave, the official Xinhua news agency said. "We fear Xinjiang is not safe any more," said one passenger who refused to be identified.

Their fear was borne out downtown. In one street, two young boys were surrounded by an angry mob, with dozens trying to pull them down and grabbing at their hair. At one point they briefly turned on a journalist.

Volatile and swelling Han crowds protested against security forces seizing young Han men.

"Why are you catching Han Chinese? They are only trying to protect us," said one woman in the crowd, bickering with police.

But the heavy security presence brought peace to central parts of the city, with armed personnel carriers standing by as helicopters hovered overhead.

Rumours swirled. A group of Uighur men said they were convinced two locals died in Tuesday's confrontations and that there were many more deaths across the city.

A man in his 50s, who gave name as Mohammed Ali, said he had heard from neighbors and friends that two men had died and two had been seriously wounded.

"Now we are scared to go anywhere," he said. "Doing even simple things becomes frightening."

"BLOOD FOR BLOOD INCOMPATIBLE WITH RULE OF LAW"

Police say Sunday's clashes were triggered by a brawl between Uighurs and Han at a factory in south China prompted by a rumor Uighurs had raped two women. Police have detained 15 people in connection with the factory brawl, including two suspected of spreading rumours on the Internet.