URUMQI, China — Violent street battles killed at least 140 people and injured 828 others in the deadliest ethnic unrest to hit China's western Xinjiang region in decades, and officials said Monday the death toll was expected to rise.

Police sealed off streets in parts of the provincial capital, Urumqi, after discord between ethnic Muslim Uighur people and China's Han majority erupted into riots. Witnesses reported a new protest Monday in a second city, Kashgar.

Columns of paramilitary police in green camouflage uniforms and flak vests marched Monday around Urumqi's main bazaar — a largely Uighur neighborhood — carrying batons, long bamboo poles and slingshots. Mobile phone service was blocked, and Internet links were also cut or slowed down.

Rioters on Sunday overturned barricades, attacking vehicles and houses, and clashed violently with police in Urumqi, according to media and witness accounts. State television aired footage showing protesters attacking and kicking people on the ground. Other people, who appeared to be Han Chinese, sat dazed with blood pouring down their faces.

There was little immediate explanation for how so many people died. The government accused a Uighur businesswoman living in the U.S. of inciting the riots through phone calls and "propaganda" spread on Web sites. Exile groups said the violence started only after police began violently cracking down on a peaceful protest complaining about a fight between Uighur and Han factory workers in another part of China.

The unrest is another troubling sign for Beijing at how rapid economic development has failed to stem — and even has exacerbated — resentment among ethnic minorities, who say they are being marginalized in their homelands as Chinese migrants pour in.

Thousands of people took part in Sunday's disturbance, unlike recent sporadic separatist violence carried out by small groups in Xinjiang. The clashes echoed the violent protest that rocked Tibet last year and left many Tibetan communities living under clamped-down security ever since.

Tensions between Uighurs and the majority Han Chinese are never far from the surface in Xinjiang, a sprawling region rich in minerals and oil that borders eight Central Asian nations. Many Uighurs (pronounced WEE-gers) yearn for independence and some militants have waged a sporadic, violent separatist campaign.

Uighurs make up the largest ethnic group in Xinjiang, but not in the capital of Urumqi, which has attracted large numbers of Han Chinese migrants. The city of 2.3 million is now about overwhelmingly Chinese — a source of frustration for native Uighurs who say they are being squeezed out.