Tibet's spiritual leader has said China is trying to "annihilate Buddhism", as the region marks the anniversary of a failed revolt against China in 1959.
The Dalai Lama's comments come as Tibetans also mark the anniversary of the bloody riots in 2008, which were crushed by Beijing.
China has stepped up security in Tibet's capital Lhasa amid fears of fresh protests, local residents say.
Beijing considers the Dalai Lama, who lives in exile, a separatist.
The Dalai Lama, who fled Tibet in 1959 and has since been living in India, says he only wants autonomy for Tibet within China.
Beijing says that rioters in Tibet killed at least 19 people in 2008, but Tibetan exiles say Chinese security forces killed dozens of protesters. It was the worst unrest in Tibet for 20 years.
In his annual address on the 51st anniversary of the Tibetan uprising, the Dalai Lama stated that "whether the Chinese government acknowledges it or not, there is a serious problem in Tibet".
"The Chinese authorities are conducting various political campaigns, including a campaign of patriotic re-education, in many monasteries in Tibet.
"They are putting the monks and nuns in prison-like conditions, depriving them the opportunity to study and practise in peace. These conditions make the monasteries function more like museums and are intended to deliberately annihilate Buddhism."
He also accused Beijing of deploying large number of troops across Tibet and placing restrictions on travel in the region.
But the spiritual leader pledged to continue his policy of "the dialogue" with China.