Lhasa has been under heavy security since the violent riots last year
The Tibetan government-in-exile has appealed to the international community to intervene in a Chinese security crackdown in Tibet's capital.
Eighty-one people have been detained and nearly 6,000 questioned in the past 11 days, Chinese state media reported.
The Tibetan Daily said the campaign in Lhasa was targeting criminals.
But the leaders-in-exile say they are concerned that China's "hardline policies" may lead to a repeat of last year's deadly anti-Chinese riots.
The centre of Lhasa has been under heavy security since last March, after peaceful protests turned violent following a military crackdown.
China said at least 18 people were killed during the unrest. Independent rights groups say about 200 people were killed and at least 1,000 are still missing.
'Fear and intimidation'
Tibet independence campaigners say China's anti-crime operation appears to be aimed at intimidating Tibetans two months ahead of the 50th anniversary of the failed uprising against Chinese rule, which led to the Dalai Lama's flight into exile.
In a statement, Tibet's government-in-exile appealed "governments and individuals around the world to actively intervene" so that "March 2008 may not be repeated again".
It also urged China to call off its crackdown, saying it had created a "heightened sense of fear and intimidation" in Lhasa and in other areas of Tibet.
It warned that the campaign would "only create an atmosphere of further political unrest" but appealed to Tibetans to remain calm despite the "harsh repression".
Tibet's leaders-in-exile fear a repeat of last year's deadly riots
The security operation - the latest to be entitled Strike Hard - began on 18 January, with raids on residential areas as well as hotels, bars and cafes, the state-run Tibetan Daily said.
Officers detained people for robbery, prostitution, theft and having "reactionary music" on their phones, it reported.
It did not say whether those detained were Tibetan, Han Chinese or of other ethnicity.
China has ruled Tibet since 1951 and views it as an integral part of Chinese sovereign territory.
It believes that the Chinese Communist Party liberated the Tibetan people from the oppressive feudal rule of Tibet's spiritual leader the Dalai Lama, following the 1959 uprising.
For Tibetan groups in exile, the events of March 1959 and the exile of the Dalai Lama were a tragedy.
The Dalai Lama has said he does not want independence for Tibet, only meaningful autonomy.