URUMQI: A China-bound Afghan plane diverted to Kandahar Sunday night after a bomb threat finally arrived at Urumqi, its scheduled destination, late last night.

Kam Air president Zamarai Kamgar, who was on the aircraft, told China Daily the entire incident "might have been a hoax". The airline's competitors might have been behind it, he said.

Kam Air is Afghanistan's first private airline. The state-owned Ariana Afghan Airlines is its primary competitor.

"I'm very confident about the Chinese market," Kamgar said, stressing that from the first week of September onwards, Kam Air will be flying Tuesdays from Kabul to Urumqi as well. Now the flight is only on Sundays.

"There was quite some confusion on the plane when we were told we had to go back," said Daud, a crew member on the flight.

"Then we realized that there couldn't be any threat; we did our best in security before the plane took off."

A source with the China Metallurgical Group Corp who flies regularly to Kabul said he shares those feelings.

"Security measures have always been super-tight. I'm guessing that this was just a trick by Ariana," he said.

The Boeing 767 flight arrived in the Afghan capital of Kabul, from which it had departed, early yesterday after an overnight stay in Kandahar, said Feda Mohammad Fedawi, deputy head of Kam Air.

Carrying 168 people, including five Chinese, the aircraft was earlier denied permission to land in Urumqi on Sunday and made an emergency landing in Kandahar during its return because "the weather condition in Kabul was very bad at that time", Kamgar said.

Pan Dongjie, a passenger on the plane, confirmed that the plane "made landing efforts in Kabul airport, but failed".

"Maybe it was because of strong winds," Pan said.

An official with Kabul International Airport, however, said the plane made the unexpected landing due to some "mechanical problem".

In Urumqi, an airport source said "the plane had descended to an altitude of about 2,000 m when it was informed by ground control that there were bombs on board and that it had to turn back".

Airport staff "received news of the bomb threat on Sunday night", according to the source. Pan, the passenger, also claims to have known about the bomb threat. But both Kamgar and Afghanistan's counterterrorism chief Abdul Manan Farahi said there was no bomb on the plane.

The airplane is scheduled to fly to Kabul from Urumqi at 10:30 am today.

Cui Jia, AP and Reuters contributed to the story