Hundreds of Chinese from rival ethnic groups fought each other with machetes, metal pipes and bricks in Urumqi, overcoming police attempts to prevent the deadliest communal clashes in decades from escalating.

A mob of Han Chinese was seen breaking into a three-story apartment inhabited by ethnic Uighurs in the northwestern city. Earlier, police fired tear gas to prevent the mob avenging rioting by Uighurs that left at least 156 dead. The fighting came after thousands of Chinese armed with knives and steel bars clashed in central Urumqi with police.

Earlier, dozens of Muslim Uighurs demanded the release of more than 1,000 people held by police following protests that left at least 156 dead. Similar scenes were played out across the city of 2.4 million, capital of the westernmost province of Xinjiang, state run Xinhua News Agency said.

The violence illustrates China's failure to address simmering grievances among its minorities, who complain of discrimination and restrictions on religious and cultural practices. Beijing's policy of investing billions of dollars to placate its restive territories of Tibet and Xinjiang has also led to a wave of migration by the Han, who make up more than 90 percent of the country's population, exacerbating tensions.

"They've pumped a lot of money in but that's not addressed any of the grievances that people have," said Calla Wiemer, a visiting fellow at the National University of Singapore's East Asian Institute. "Questions of identity and practice of culture and religion and opportunity have not been addressed by money."

Uighur Population

Muslim Uighurs, who now make up less than half Xinjiang's 20 million population after years of Han migration, complain of discrimination and unfair division of the region's resources. The landlocked region, about three times the size of France, has China's second-highest oil and natural gas reserves and was the biggest cotton producer.

"Uighurs feel they are not getting enough of the goodies," said Professor Colin Mackerras, a China expert at Australia's Griffith University in Queensland. "The balance has shifted quite heavily in favor of the Han and the Uighurs think they are being taken over."

President Hu Jintao, 66, who administered Tibet between 1988 and 1992, hasn't commented on the events. Tibet was struck by rioting in 1989. Hu is preparing to meet leaders of the Group of Eight nations in Italy this week. The U.S. and Japan have both expressed concern at the deaths of civilians.

Overseas Separatists

China's Foreign Ministry today again blamed overseas separatists for fomenting the riots, branding them terrorists and criminals. The riots two days ago were a premeditated attack, spokesman Qin Gang told a briefing in Beijing today. "Their terrorist nature will be exposed to the world," he said.

The World Uyghur Congress, a Munich-based exile organization that seeks independence from China, rejected the accusation.

Authorities made mass arrests, deployed 20,000 security personnel and cut internet and phone lines to stem the violence. A curfew in Urumqi has also been put in place for tonight, Xinhua said.

Urumqi Communist Party chief Li Zhi today addressed the Han demonstrators from the roof of a car, urging them to disperse and trust the government. Protesters attacked Uighur property, sang the national anthem and ripped down posters exhorting residents to preserve social harmony.

Police Road Blocks

Police set up road blocks to keep the protesters away from Uighur areas.

The latest protests followed reports that most of the victims in the earlier rioting were Han. Of the 274 people being treated in Urumqi's People's Hospital, 233 were Han, the Hong Kong-based South China Morning Post reported, citing the head doctor, whom it didn't name.

Protests spread to the Uighur-majority oasis town of Kashgar yesterday, the state-run Xinhua news agency reported. Several hundred demonstrators gathered in the outpost on China's western border, before dispersing as police began making arrests, the New York Times said, citing a resident it didn't identify.

Control

"The government feels that if they don't control it immediately and harshly it will get out of control," said Dru Gladney, president of the Pacific Basin Institute at Pomona College in Claremont, California.

The official death toll makes the violence the most deadly in decades, possibly since the Cultural Revolution.

The official death toll in the demonstrations that broke out in Lhasa, capital of Tibet, in March last year was 19. Unofficial estimates put the toll at about 200. The government cast those riots as Tibetan violence directed at Han Chinese and Hui, a minority group that is ethnically similar to the Han.