URUMQI, China (Reuters) - Chinese police dispersed 200 people gathering outside a mosque in the Silk Road city of Kashgar, the day after ethnic riots killed 156 in the capital of the Muslim Xinjiang region, state media said on Tuesday.

Calm had settled over Urumqi, capital of western Xinjiang region, after 20,000 police, troops and firefighters reclaimed the streets from rioters who burned and smashed vehicles and shops, and clashed with security forces over Sunday night.

Over 700 people had been detained, the official Xinhua news agency reported, although local residents told Reuters police were making indiscriminate sweeps of Uighur areas.

But despite heightened security some unrest appeared to be spreading in the volatile region, where long-standing ethnic tensions periodically erupt into bloodshed.

Police dispersed around 200 people “trying to gather” at the Id Kah mosque in the center of Kashgar city on Monday evening, the day after the Urumqi rioting, Xinhua said. Kashgar is in the far west of Xinjiang.

The report did not say if police used force, but said checkpoints had been set up at crossroads between Kashgar airport and downtown.

Police also had “clues” about efforts to organize unrest in Aksu city and Yili prefecture, the latter a border region that was racked by unrest in the late 1990s, Xinhua said.

Along with Tibet, Xinjiang is one of the most politically sensitive regions in China and in both places the government has sought to maintain its grip by controlling religious and cultural life while promising economic growth and prosperity.

But minorities have long complained that Han Chinese reap most of the benefits from official investment and subsidies, while making locals feel like outsiders in their own homes.

Almost half of Xinjiang’s 20 million people are Uighurs, while the population of Urumqi, which lies 3,270 km (2,050 miles) west of Beijing, is mostly Han Chinese.

Chinese officials have already blamed the unrest on separatist groups abroad, who it says want to create an independent homeland for the Muslim Uighur minority.

A Xinjiang public security spokesman told Xinhua that people outside China used telephones to “direct mobs in Xinjiang to stage the violence,” and said calls for protests were posted Saturday evening on Internet forums by sympathizers.

Last year, Beijing also blamed unrest across Tibetan areas on a “clique” led by the exiled Dalai Lama.

But exile groups deny organizing the violence and say it was an outpouring of pent-up anger over government policies and Han Chinese economic dominance.

In Washington, the White House said it was concerned about the deaths but it would be premature to speculate on the circumstances. “We call on all in Xinjiang to exercise restraint,” White House spokesman Robert Gibbs said.

CHASM BETWEEN SIDES

Muslim Uighur and Han Chinese residents of Urumqi gave accounts of bloodshed that are likely to deepen the chasm between the two sides.

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Uighur residents, speaking softly in alleyways away from patrolling police and troops, complained about the growing Han Chinese presence. Some said many of those arrested were youths caught up in indiscriminate police sweeps of the rundown concrete apartments where many Uighurs live.

“They’ve been taking away all the young people, going into our homes and taking them away,” said Amina, a middle-aged woman in a Muslim headscarf sitting on the steps of a mosque. She said her own son had been taken but did not want to give his name.

“They don’t care who they take, as long as you’re between 17 and 20 and they don’t like the look of you,” she said as her neighbors shook their heads and clucked in sympathy.

Nearly all Uighurs traced the protests on Sunday back to their own anger over a confrontation in far southern China in late June, when Han Chinese fought Uighurs working in a factory in Shaoguan, leaving two Uighurs dead, after a false allegation that some of them had raped a Han Chinese woman.

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The government said two Uighurs died in that clash. But many Uighur residents of Urumqi said they were sure that many more died at the factory, and gave vivid accounts of how 20, 50 or a 100 of the workers were killed in their sleep -- stabbed, strangled or poisoned. And some said a Uighur woman was raped.

There is no independent evidence to support those claims, but Uighur residents said they were angry the details of the factory clash were not more fully aired by the government.

“We know that 100 workers were killed,” said a young Uighur, who gave his name as Memet. “Now who cares about their deaths? Why all these police for us, but nothing when they died?”

Han Chinese residents said the toll from the riots was likely to rise and their deepened fears of the Uighurs were unlikely to abate.

Chen, a driver, said his wife who shares driving duties with him had suffered a badly cut eye when a Uighur youth attacked their car, and now she was afraid to venture far from home.

“Why doesn’t the United States classify them as terrorists?,” said Chen, who would not give his full name. “What they did to us is terrorism, isn’t it?”

He said the rioters appeared to be mostly Uighur men in their twenties, many of them unemployed. Riot victims recovering in a Urumqi hospital described groups of men who targeted Han Chinese and attacked them with purposeful efficiency.

“They didn’t really talk to you,” said Huan Zhangzhao, with two broken ribs and a bloodied eye. “When they saw you, when they saw a Han person coming along, they started to attack. When a bus came along, they started to attack.”