China thwarted an attempt to down an internal passenger flight en route to Beijing last week, a top regional official said yesterday. China Southern flight CZ6901 made an emergency landing in Lanzhou, capital of Gansu at about 12.40pm on Friday after departing from Urumqi airport in Xinjiang at 10.35am, Xinjiang region chairman Nuer Baikeli said. All passengers and crew were unharmed and the plane flew on to Beijing on Saturday morning after being held at Lanzhou military airport for several hours. Airline sources said four Uygurs, some who were not Chinese nationals, were taken away by police for questioning after the plane landed. One, a woman, had taken cans of petrol into a toilet, where she remained until passengers and crew noticed the smell of petrol and took action. 'One thing that we are now certain of is this was an attempt to create an air disaster,' Mr Baikeli said on the sidelines of the National People's Congress. He said the identities, background or motives of the attackers were unavailable as an investigation was still under way. Revelations of the plane attack, an extremely unusual event in China, came as Xinjiang leaders pledged yesterday to step up efforts to nip terrorist activities in the bud in the run-up to the Olympic Games. Wang Lequan, Xinjiang's party chief, said yesterday that a terrorist group broken up in the Xinjiang capital, Urumqi, in January had plotted to sabotage the Olympic Games in August. It was unclear if the apparent attack on the airliner last week was linked to the Olympics but it took place just as China's top officials and legislators gathered in Beijing for the annual National People's Congress.