Authorities have boosted security in Urumqi as the northwestern Chinese city prepares to host the first China-Eurasia Expo, where leaders of China and its neighbors in central and south Asia are expected to attend.

Fully-armed police carrying rifles were seen guarding the convention venue located in suburban Urumqi, capital of Xinjiang Uygur Autonomous Region, on Tuesday, two days before the official opening. S.W.A.T. units were deployed to handle the security check at the entrance.

The authorities declared a low-altitude "no flight zone" in areas around Urumqi that effectively bans anything from light aircraft to hot-air balloons during the expo. No pigeon flying is allowed either.

Airports in a dozen cities, including Beijing and Shanghai, have tightened security screenings for Urumqi-bound flights since Sunday. Passengers are asked to remove their shoes and have their take-on luggage open.

The increased security comes amid a two-month crackdown on terrorism ordered by regional authorities earlier this month following a spate of violence in two major southern Xinjiang cities, which left at least 40 dead and dozens injured. A unit of the Snow Leopard Commandos, an elite counter-terrorism force under the People's Armed Police, has been deployed from Beijing to the region.

"Security is paramount," said Yu Xiudong, a senior member of the expo organizing committee, on Tuesday. "We should make meticulous preparations against all security emergencies to ensure a safe expo."

Xinjiang -- with 41.5 percent of its 21 million population Uygur, a largely Muslim ethnic group -- has been battling separatism, extremism and terrorism for decades.

A deadly riot hit Urumqi two years ago, leaving 197 dead and about 1,700 others injured. Bag checks and car trunk inspections in public places have become part of people's daily routine in the city.

After the riot, the central government implemented a series of policies to boost economic development in Xinjiang, hoping that the rise in living standards and prosperity could eliminate the root of violence.

The expo was upgraded from a regional trade fair, the 19-year-old China Urumqi Foreign Economic Relations and Trade Fair, last year. Organizers said the upgrade would make Urumqi an important exchange platform for leaders and businesses of China and its western and southern neighbors, such as Russia, Kazakhstan, and Pakistan.