URUMQI, CHINA, AND BEIJING — In an escalating campaign to stamp out ethnic violence, Chinese forces Wednesday saturated the northwestern city of Urumqi, helicopters dropped leaflets urging calm, and the local Communist Party boss warned of the death penalty for rioters convicted of killings.
"We're determined to maintain social stability," said Urumqi's party chief, Li Zhi, at a news conference. "To those who committed crimes with cruel means, we will execute them."
In spite of the massive show of force, Han Chinese and the Turkic minority Uighurs continued to duke it out in the city streets, showing how difficult it will be to restore order.
Since Sunday, violence has virtually paralyzed Urumqi, a city of 2 million, and authorities fear it could easily spread to other parts of the Xinjiang region, particularly the southern cities of Hotan and Kashgar, which have Uighur majorities.
"Many people think it has calmed down, but we worry it is just the beginning," said a public security official, who spoke Wednesday on the condition of anonymity.
"This is a huge threat to national harmony. It is the most serious violence we have seen since the 1980s."
The Chinese government has not reported any casualty figures since Monday, when it said 156 people had been killed in rioting in Urumqi, the regional capital, the previous evening. Security officials said it had been decided to hold off further reporting for fear of inflaming the violence.
The seriousness of the crisis was highlighted by Chinese President Hu Jintao's abrupt return to Beijing on Wednesday, canceling his appearance with other world leaders at a summit of the Group of 8 industrial nations in Italy.
With bands of Han Chinese vigilantes roving the streets carrying crude weapons and swearing revenge against attacks on their people over the weekend, Chinese authorities were not taking any chances.
Thousands of police -- some in full body armor, some carrying machine guns and shotguns, others crossbows -- guarded main thoroughfares, city squares and alleyways leading to Uighur enclaves.
Still, one man believed to be Uighur was attacked on a street by an angry mob outside a closed store. The victim on North Jiefang Road was punched and kicked repeatedly, his head bashed against the curb.
Within minutes, authorities arrived and pushed back the crowd. Officers formed a phalanx to arrest a man who appeared to be one of the attackers. A large group of young Chinese men chanted, "Release him! Release him!" It was unclear what happened to the suspect.
A police truck with loudspeakers arrived behind the crowd and played a looped recording that told the crowd to go home.
"Xinjiang is a place for all ethnic groups," the recording said.
A helicopter then flew over, dropping bundles of single-page leaflets onto the crowd -- copies of a speech made by the regional Communist Party chief calling for calm and ethnic unity.
In another incident earlier in the day, three Uighurs were chased by Han Chinese at an intersection. Two got away, but one was beaten for 30 seconds by a crowd -- some of whose members shouted, "Strike! Strike! Strike!" -- before being rescued by police, according to Agence France-Presse.
The agency also reported that about 200 Uighurs armed with sticks, pipes and rocks demonstrated in front of a police cordon after trading insults with Hans on the opposite side.
The rioting broke out Sunday after what was supposed to be a peaceful march by Uighurs protesting the killing last month of two Uighur men at a factory in southeastern China's Guangdong province. It is unclear how many of the 156 people reported killed that day were Han; Chinese authorities have not released names of the victims.
In many neighborhoods of Urumqi there was evidence of the violence: shops and restaurants destroyed, a brand-new supermarket with all its windows shattered. The remains of two Han-owned car dealerships, charred black with overturned sedans, faced a desperately poor traditional Uighur neighborhood.
"I saw a mob with sticks and rocks beating people. I think they killed someone outside my business," said Wang Hua, 26, pointing to dried blood splattered on the wall of his auto parts store.
"It was a bunch of jobless hooligans. They knew my store was Han."
Nearby, men squatted on the dusty pavements, shielding their eyes from sand kicked up by cars driving down unpaved alleyways. Many could barely speak Chinese.
Hiu Wenbin, a 25-year-old taxi driver, said economic resentment had fueled the violence.
"You see so many unemployed Uighur men. . . . There are more and more Han people doing business here. . . . They don't really hire Uighur people."
"This won't die down," Hiu said of the violence. "I don't see either side letting it go. These Uighurs see how rich these Han business owners are -- of course they want to burn their places down."