The leader of Tibet's government-in-exile is calling for foreign intervention to prevent further bloodshed after reports that Tibetan protesters were killed by police during two days of clashes in China's southwestern Sichuan province.

In a statement released Wednesday, exiled Tibetan Prime Minister Lobsang Sangay said the international community must take a “moral stand” and could “not remain passive” in the face of the violence.

The London-based Free Tibet organization said at least two people were shot dead and many others wounded during a protest Tuesday in Seda County. A day earlier, the group said security forces killed two Tibetans and wounded 36 others who were protesting religious oppression in the nearby town of Luhuo.

China's state-run Xinhua news agency on Wednesday acknowledged the clashes, but said police were forced to open fire after a “mob” attacked police with guns, knives, stones, and bottles. The report said one protester was killed and another wounded during Tuesday's clashes.

Hundreds of exiled Tibetans and Buddhist monks held public prayers Wednesday in the northern Indian town of Dharamsala. The former speaker of the Tibetan parliament-in-exile, Karma Choephel, condemned the killing.

The reports of violence follow the self-immolation of four Tibetans earlier this month. A total of 16 Tibetans have set themselves on fire to protest Chinese rule since March of 2011.

On Tuesday, the U.S. Special Coordinator for Tibetan Issues, Maria Otero, said Washington was “gravely concerned” about the reports of violence. The State Department also called on the Chinese government to exercise restraint and open dialogue with Tibet's exiled spiritual leader, the Dalai Lama.

The Chinese Foreign Ministry said widespread reports of unrest and violence in Sichuan are exaggerated, and that the protest on Monday involved dozens – not thousands – of demonstrators. It said the demonstrations were spawned by “overseas secessionists.”