China has detained nine Buddhist monks and accused them of planting a homemade bomb last month in a government office building in eastern Tibet, an official said Sunday.

There were no known deaths or damage from the first reported bombing since anti-government protests by monks began March 10 in the Tibetan capital Lhasa.

The official Xinhua News Agency said the monks from the Tongxia monastery fled after a bomb exploded in Gyanbe township on March 23. They later confessed to planting the explosive, Xinhua said.

Xinhua did not explain why the alleged incident was not reported earlier.

An official with the local Gongjue county Public Security Bureau confirmed the report and said six monks had been detained for planting the bomb and three for shielding the suspects and covering up their crimes. The man refused to give his name because he was not authorized to talk to the media.

The alleged bombing builds on Beijing's claims that the recent protests were part of a violent campaign by Tibet's exiled spiritual leader, the Dalai Lama, and his supporters to overthrow Chinese rule in Tibet and sabotage the Beijing Olympics in August.

Scholars say China's accusations help the government justify its crackdown and demonize the opposition while driving a wedge between the government-in-exile and groups like the Tibetan Youth Congress that have challenged the Dalai Lama's policy of nonviolence.

The protests in Lhasa turned violent on March 14, with hundreds of shops torched and Chinese civilians attacked. China says 22 people were killed in the riots, and more than 1,000 have already been detained.

Earlier this month China accused Tibet independence forces of organizing suicide squads to launch violent attacks against China. Wu Heping, spokesman for China's Ministry of Public Security, also claimed searches of monasteries in the Tibetan capital had turned up a large cache of weapons.

On Friday, China labeled a group linked to the Dalai Lama's India- based government-in-exile a "terrorist organization."

Separately, Xinhua said Saturday that a Tibetan taken into custody in a Lhasa monastery had confessed to slashing a passer-by three times with a knife during the March 14 riot. The man was listed as No. 2 in a most-wanted list by police, Xinhua said.

Police have 93 suspects on the list and have arrested 13 of them, Champa Phuntsok, the Chinese-appointed head of the Tibetan Autonomous Region said last week.

Xinhua News Agency accused the Tibetan Youth Congress of planning the riots in Lhasa. As evidence, Xinhua cited alleged statements and speeches by Youth Congress leaders, as well as a purported plot to smuggle weapons into Tibet to launch attacks. The allegations were impossible to verify.

The Tibetan Youth Congress has said China's communist leadership had long sought to destroy its effectiveness by smearing its reputation.

In his first public comments on the protests, Chinese President Hu Jintao took a hard line Saturday on the unrest in Tibet, saying problems in the region are an internal affair that directly threatens Chinese sovereignty.

"Our conflict with the Dalai clique is not an ethnic problem, not a religious problem, nor a human rights problem," Xinhua quoted Hu as saying, referring to supporters of the Dalai Lama. "It is a problem either to safeguard national unification or to split the motherland."