BEIJING — Chinese police killed alleged terrorists plotting to attack the Beijing Olympics, while a flight crew managed to prevent an apparent attempt to crash a Chinese jetliner in a separate case just last week, officials said today.

Wang Lequan, the top Communist Party official in the western region of Xinjiang, said materials seized in a January raid in the regional capital, Urumqi, had described a plot with a purpose "specifically to sabotage the staging of the Beijing Olympics."

"Their goal was very clear," Wang told reporters in Beijing.

Wang cited no other evidence and earlier reports on the raid had made no mention of Olympic targets.

Speaking at the same meeting, Xinjiang's governor said a flight crew prevented an apparent attempt to crash a China Southern flight from Urumqi on Friday. Nur Bekri did not specifically label the incident a terrorist act, saying it remained under investigation. No passengers were injured and police were investigating, he said.

China has ratcheted up anti-terror preparations ahead of the August Games, with the nation's top police official last year labeling terrorism the biggest threat facing the event.

Police found guns, homemade bombs, training materials and "extremist religious ideological materials" during the Jan. 27 raid in Urumqi, in which two members of the gang were killed and 15 arrested, according to earlier reports.

Chinese forces have for years been battling a low-intensity separatist movement among Xinjiang's Uighurs, a Turkic Muslim people culturally and ethnically distinct from China's Han majority. Iron-fisted Chinese rule has largely suppressed the violence, however, and no major bombing or shooting incidents have been reported in almost a decade.

Wang said the group had been trained by and was following the orders of a Uighur separatist group based in Pakistan and Afghanistan called the East Turkestan Islamic Movement, or ETIM. The group has been labeled a terrorist organization by both the United Nations and the United States. East Turkestan is another name for Xinjiang.

China says its main terror threat comes from ETIM. Although the group is not believed to have more than a few dozen members, terrorism experts say it has become influential among extremist groups using the Internet to raise funds and find recruits.

Wang said security forces would take pro-active measures to crush terrorism, religious extremism, and separatism.

"These guys are fantasizing if they think they can disrupt the Olympics," said Wang, known for his hardline stance on crushing dissent. "They don't have the strength."

Few details were available about the alleged attempt to crash the China Southern Airlines flight that left Urumqi at 10:35 a.m. on Friday.

Bekri, the governor of the Xinjiang region, indicated that more than one person was involved, but did not specify who was suspected to be behind the attempt, saying it remains under investigation.

"From what we presently know, this was an attempt to crash the plane," Bekri said.

Bekri said the crew responded and brought the plane to an emergency landing in the western city of Lanzhou at 12:40 p.m. No passengers were injured and police were investigating, he said.

He said it continued to its original destination, Beijing, after about one hour.

A man who answered the phone at China Southern's Urumqi office said he the incident was under investigation and he had no further details. He hung up without giving his name.