Passengers were stranded at Beijing Capital International Airport (BCIA) as the security measures were suddenly increased to a level of security not normally observed for domestic flights. Photo: CFI.cn

Sudden increased security measures at Beijing Capital International Airport (BCIA) disrupted the travel plans of thousands of passengers during Sunday's morning rush, causing security checks to take hours longer than usual with many people missing their flights.

Passengers were told to remove their shoes and belts at checkpoints, a level of security not normally observed for domestic flights.

Slow-going through security reportedly caused crowds to begin forming at around 5 am at the airport.

Pictures uploaded to social networking sites by angry passengers showed thousands outside security checking areas in Terminal 3.

Gao, a university professor who refused to give his full name, told the Global Times that he missed his flight to Hohhot, Inner Mongolia Autonomous Region because many passengers were not ready for the tightened security.

"They even asked me to remove my pants," Gao said, adding that he had not been informed of the security upgrade.

It took Gao 70 minutes to pass through security at 7:10 am. He caught a second flight out at 10:20 am, after hours of waiting and losing 600 yuan in the crowd.

At least 1,000 passengers missed their flights or were kept waiting for hours at BCIA, Weibo users claimed, but the exact number of people or flights affected could not be verified.

Traffic at the airport appeared to have returned to normal by 1 pm on Sunday.

"There is no need to put the airport on special notice since it is functioning normally," an anonymous source at the BCIA told the Global Times on Sunday.
A similar order for heightened security was also received in Shanghai on Sunday morning, Tian Lu, a press officer with the Shanghai Airport Authority, told the Global Times.

The Shanghai-based Xinmin Evening Post warned that passengers at the city's Pudong and Hongqiao airports would have to remove belts and shoes because "airports across the nation have raised their security level today."

However, security procedures at Xiaoshan Airport in Hangzhou, Zhejiang Province remained as usual on Sunday, the airport's customer service desk told the Global Times.

By press time, the Civil Aviation Administration of China did not release any information about the security upgrade.

Online speculation suggested that the security boost was in response to a foiled terrorist attack attempt last month at Urumqi airport, Xinjiang Uyghur Autonomous Region that allegedly saw suspects hide daggers inside walking canes.

Rumors said Xinjiang police had destroyed "a gang of dozens planning suicide attacks on airplanes," and airports across China are "responding to a mandate of the Civil Aviation Administration of China to tighten security."

However, Xinjiang government press chief Hou Hanmin denied all speculations about the thwarted attacks on Sunday.

"(Such things) didn't happen," she told the Global Times.

An official at the BCIA press center confirmed with the Global Times that the airport was heeding a security order from "higher authorities," but refused to explain why the order was given, citing the "sensitive nature of the matter."

Xinjiang was hit by three riots in July in Hotan and Kashi, during which more than 15 people were killed.

The airport of Urumqi has enforced tightened security checks since early August, ahead of the China-Eurasia Expo that runs from Thursday to September 5.

Passengers must go through two rounds of checks: upon entering the terminals and then at the normal security check, where they are asked to remove their shoes and belts.

Electronic devices are allowed in carry-on luggage, but lithium batteries must be taken out and carried separately, according to the customer service at the airport.

Less lethal items have been caught at Urumqi Diwobao International Airport recently.

On Friday, a woman trying to board Flight SC4634 to Qingdao was found carrying a tear gas device, the airport said on its official website.

Miranda Shek in Shanghai, Liu Linlin and Huang Jingjing in Beijing contributed to this story