As Urumqi braces for a five-day trade fair, China says it has foiled "terror" plots by extremists during a visit by Pakistani President Asif Ali Zardari.
The Pakistani leader had traveled to the troubled northwestern region of Xinjiang to celebrate the end of a traditional month of fasting alongside Uyghur Muslims.
Zardari attended the Eid prayer alongside Uyghur worshipers and his own high-ranking officials in charge of commerce, defense,and natural resources, local media reported.
But an exile Uyghur group said the Turkic minority Uyghurs were themselves subject to tight controls during the Eid al-Fitr celebrations, which mark the end of the fasting month of Ramadan with prayers and feasts.
Dilxat Raxit, spokesman for the Munich-based World Uyghur Congress, said controls and surveillance had been stepped up on the region's Muslim Uyghur people, many of whom are unhappy with Chinese rule and call for the right to "self-determination."
"In Kashgar, Hotan, and Aksu in the south, and in Ili in the north, there has been increased surveillance in mosques during Eid al-Fitr," Raxit said.
"The authorities have also intensified their 'clean-up' campaign, even going so far as to offer rewards for any information about illegal religious texts coming in from elsewhere in the region," he said.
"Anyone who gives relevant information can receive different payments of varying amounts."
Raxit said the authorities had rounded up an estimated 200 people ahead of the Expo, most of them Uyghurs.
"A lot of people have been detained, or, if they were released, then they would be designated 'key characters' and forcibly 'disappeared,'" he said.
China has blamed religious extremists and terrorists 'trained in Pakistan' for a string of violent incidents to hit Xinjiang.
As regional leaders attended the opening ceremony of the China-Eurasia Expo in the regional capital, Urumqi, police said they had thwarted "several attempts to sabotage public safety" ahead of the event.
Urumqi Party boss Zhu Hailun told reporters that separatists, religious extremists, and terrorists have been plotting to sabotage the expo, the official Xinhua news agency reported.
According to Zhu, airport security staff in Urumqi on Aug. 7 arrested a man carrying a knife, on suspicion of planning to carry out an attack on the flight.
"There have been many similar cases of attacks being blocked by police," the agency quoted Zhu as saying.
Beijing is ramping up security for the trade fair in Urumqi, where deadly ethnic riots killed at least 197 people two years ago.
The convention center in suburban Urumqi was guarded by police carrying rifles, while S.W.A.T. units were deployed to handle the security check at the entrance, official media reported.
An Urumqi resident surnamed Li said the authorities had set up a security cordon with traffic checkpoints around the city for the duration of the five-day expo, which Beijing has billed as an opportunity to develop trade and economic cooperation between Central Asian economies.
Other residents blamed citywide traffic holdups on passing motorcades for visiting leaders from Beijing and overseas heads of state.
"When the leaders come, they put traffic controls everywhere," said a resident surnamed Zhang. "When foreign officials come, they put security cordons everywhere."
"The intersections have all been sealed off," he said. "We can't move until they've gone. Everyone is saying that there are security cordons everywhere."
"A lot of people are staying at home," Zhang said.
A second resident surnamed Wu said most people had learned of the traffic restrictions via popular microblogging services.
"Wherever the officials go, there you will have security cordons and restrictions," he said. "Netizens have been exchanging information with each other about which areas have been sealed off, and where the traffic is jammed."
Wu said many people had reported missing flights or train connections.
"Now you have to get to the airport three hours ahead of your flight, and if there's a traffic jam on the way and added security, it's very easy to miss the flight ... or train."
A source in the tourism industry surnamed Han said the expo had hit tourism badly, with visitor arrivals falling by around 90 percent in recent days.
"There has been a huge impact," Han said. "The government has taken over all hotels of three stars and upwards, so there's nowhere for people from out of town to stay."
"Only the smaller, independent hostels are still open for business."
An Urumqi resident surnamed Yao said several hundred factories in the immediate vicinity of the expo venue had stopped production.
"There are around 300 businesses in the Qidaowan industrial park that have been closed down during the Expo," he said. "They aren't allowed to operate."
"We don't know the reason the government has done this, but it's not far from the Hongguangshan No. 3 New Exhibition Center," he said, referring to the venue for the Expo.
Kyrgyz President Roza Otunbayeva, Azerbaijan's vice premier Abid Sharifov, and Kazakhstan's deputy prime minister Aset Isekeshev also attended the fair's opening.
Official media say Beijing wants to turn Urumqi into an important exchange platform for leaders and businesses in China and its western and southern neighbors, including Russia, Kazakhstan, and Pakistan.
But some experts say Beijing's rapid development of Xinjiang, which they say has created more opportunities for Han Chinese than the local Uyghur population, is leading to additional ethnic tension in the region.
Reuters reported that Uyghur-owned businesses were noticeably absent from the China-Eurasia Expo, which runs from Sept. 1-5.
Uyghurs the news agency spoke with said they had little money for advertising and were unable to market outside of Xinjiang, adding that most of the regional businesses at the expo were Han-owned.
Most Uyghurs at the trade fair appeared to be either reporters for state-owned media or government officials, Reuters said.
Reported by Qiao Long for RFA's Mandarin service and by Hai Nan for the Cantonese service. Translated and written in English by Luisetta Mudie.