A video grab of Shenzhou-9 spacecraft launch featuring the two flying objects. [Photo: Agencies]

Chinese experts can't fully explain the two glowing unidentified flying objects which appeared to be rushing at high speed toward Shenzhou-9 spacecraft shortly after its launch on Saturday.

However, one did raise the possibility that it could just have been two moths flying in front of a camera lens.

It has been confirmed that the objects were recorded by one infrared video camera monitoring the launch and were spotted on a screen at a control center in Beijing about four minutes after the Long March-2F rocket had blasted off from the Jiuquan Satellite Launch Center in northwest China's Gansu Province.

The rocket had just shed its nose cone when they were seen heading toward the rocket before flying past and vanishing two seconds later.

Many television viewers saw the objects during a live broadcast on state TV.

"They couldn't be planes, meteors, birds or separated parts from the rocket," Wang Sichao, an astronomer and UFO expert at the Nanjing Purple Mountain Observatory of the Chinese Academy of Sciences, said in an early assessment. However, later he conceded that were two possibilities. They could be two moths flying dozens of meters away past the camera lens. And they also might have been planes, if the rocket had flown past the no-fly zone by the time the two objects were captured.

"If the two objects, emitting light, had been detected at different locations, they could have been UFOs," Wang told China News Service. "But (we) haven't received a similar report at another location yet."

Wang ruled out spots on the camera lens or meteors.

He said the video would be kept in the archives for further research.

The Shenzhou-9 spacecraft took off from the launch site in the Gobi Desert at 6:37pm on Saturday.

A video of the launch featuring the two flying objects was posted on Weibo and by Tuesday afternoon had received more than 2,000 comments.

Many people said the objects might have been planes flying beside the rocket or parts of the rocket itself.

Wang said they couldn't be rocket parts as they were flying in the wrong direction - toward, not away from, the rocket. Planes were a distant possibility early in the launch because there were air traffic restrictions in place around the launch site.

An astronomy expert in Shanghai said the infrared video shot from a single spot offered too little information to identify the objects.

"We need the videos from at least two cameras from different angles to work out the precise position and speed of the objects and then to identify what they were," said Tang Haiming, an official with the Shanghai Astronomical Observatory on Sheshan Hill.

Last August, a huge glowing object was spotted high above Shanghai, Beijing and other regions in China by several civil aviation pilots, sparking debate among astronomers.

Some said the object was an aircraft beyond human technology after studying pictures and calculating its flight path.

The Shenzhou-9 and its crew of three, flight leader Jing Haipeng, 45, Liu Wang, 43, and China's first female astronaut Liu Yang, 33, successfully linked up with the Tiangong-1 space lab on Monday.