By Nick Mulvenney

BEIJING, March 12 (Reuters) - Chinese President Hu Jintao's likely successor and the nation's domestic security chief have been charged with overseeing the last few months of preparations for the Beijing Olympics, a senior official said on Wednesday.

The announcement came on a day when the foreign minister denounced outside interference in the Olympics, illustrating how important a safe and successful Games is to China, and a day after hundreds of monks took part in rare street protests in Tibet.

Xi Jinping, who is likely to replace Hu in 2012, and Zhou Yongkang, the Party's security tsar, will join top Beijing organiser Liu Qi in the Olympics and Paralympics leadership small group, Beijing vice-major Liu Jinming said.

"In January, the Central Party Committee ... decided to launch a leading committee of Beijing Olympics and Paralympics, which is headed by comrade Xi Jinping, and deputies Zhou Yongkang and Liu Qi," he told a news conference on the sidelines of the annual meeting of China's parliament.

"The launch of this committee will strongly support and powerfully push forward the final period of preparations for the Olympics."

China has been subjected to an intensified barrage of criticism over the last year from rights groups concerned with issues from Darfur to Tibet who hope to leverage the Olympics to alter Chinese policy.

Foreign Minister Yang Jiechi told the critics to back off, accusing them of violating the Olympic Charter, which calls for the separation of politics and sports.

"I don't believe that the international community wants to politicise the Beijing Olympics," Yang told reporters. "That's a handful of individuals and forces extremely unfriendly to China and bearing massive prejudices."

China welcomed "well-intentioned" criticism of the Games, he said. "But those who want to tarnish China -- and hear me, I said China -- won't succeed."

Concern about security around the Games was stirred this week when Chinese officials announced a domestic flight from the restive western region of Xinjiang was grounded over fears of a terrorist attack.

On Tuesday, thousands of Chinese security personnel fired tear gas to try to disperse more than 600 monks taking part in a second day of rare street protests in Tibet, a source and Radio Free Asia said.

The Tibet demonstrations follow a string of marches around the world to commemorate the 49th anniversary of an uprising against Chinese rule in the remote, mountainous region that has become a flashpoint for protesters ahead of the Games.

SAFE AND CLEAN

Yang said the Chinese capital would be safe and clean for visitors and the event would seal, not sour, friendly ties.

"China of course is one of the safest places in the world," he added.

Two days after Ethiopia's marathon world record holder Haile Gebrselassie said he would not run the endurance event in Beijing over pollution concerns, there were more details of how the city plans to guarantee clean air during the Aug. 8-24 Games.

Another Beijing vice-mayor, Ji Lin, said the city would take cars with odd and even-numbered licence plates off the roads on alternate days and confirmed the plan would go into operation in July.

Ji said the restrictions, likely to take nearly half of the city's 3.3 million cars off the roads, would also hit government departments and companies.

"Some will put 50 percent of their cars away, some will put 70 percent of their cars away," Ji told a news conference.

"When this traffic scheme is put in place, we have a guiding principle, to do our best to reduce the inconvenience on normal work and life," Ji said, adding that compensation measures were being considered. (Additional reporting by Chris Buckley and Ian Ransom; Editing by Jeremy Laurence) (Take a look at the Countdown to Beijing blog at http://blogs.reuters.com/china)

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