By Michael Bristow
BBC News, Beijing
China has often accused the Dalai Lama of fomenting trouble
China claims that Tibetan "independence forces" are planning to launch suicide attacks as part of a wider uprising to establish an independent Tibet.
Public Security Ministry spokesman Wu Heping said these suicide squads "fear neither bloodshed nor sacrifice".
Mr Wu did not produce any evidence to back up the claims - but said China would release proof later.
The prime minister of the Tibetan government-in-exile, Samdhong Rinpoche, denied China's allegations.
Mr Wu claimed the wave of protests that erupted across Tibetan areas recently was part of a "Tibetan People's Uprising Movement" ahead of the Olympic Games.
He said police had recently discovered guns, ammunition, knives and explosives in the dormitories of Tibetan monks.
Mr Wu's comments mark a dramatic increase in the seriousness of the accusations against Tibetans and, by extension, the Dalai Lama, the head of Tibetan Buddhism.
"To our knowledge, the next plan of the Tibetan independence forces is to organise suicide squads to launch violent attacks," he said at a press conference.
He went on to say that the recent anti-Chinese demonstrations by Tibetans were part of a well-thought-out plan to split Tibet and China.
"Back in 2007 the Tibetan independence forces in the United States plotted this very concept," he told journalists.
"They believe it will be their last chance to realise Tibetan independence," he added, referring to the publicity this group could attract ahead of the Olympic Games.
Mr Wu said these plotters had consulted with the "Dalai clique".
The Dalai Lama has consistently denied organising the unrest, and threatened to resign as the spokesman for the Tibetan government-in-exile if it did not stop.
He fled Tibet in 1959 after a failed uprising against Chinese rule.
But China says the Dalai Lama's calls for an end to violence are "blatant lies" that are aimed at masking his real intention.
In order to fulfil his separatist plans, Chinese police claim the Dalai Lama set up an intelligence network in Tibet to collect and disseminate information.
Secret activists used code to talk about sensitive topics, according to Mr Wu, with the Dalai Lama apparently referred to as "uncle".
Mr Wu said police have arrested a "key member" of this network who confessed to being involved in separatist activities.
They have also confiscated 176 guns, 13,000 rounds of ammunition and more than 3,500kg of explosives, he added.
China says 18 civilians and two police officers died in the unrest in Tibetan and neighbouring provinces inhabited by Tibetans that began on 10 March.
Tibetan groups outside China put the death toll at up to 140, a figure that includes Tibetans they say were killed by Chinese security forces.
All claims about the unrest are difficult to verify because the Chinese government has mostly barred foreign journalists from these sensitive areas.