One of the photos released by Tibetan Center for Human Rights and Democracy

Human rights groups have released photographs that show Tibetans allegedly shot and killed by security forces in China's western province of Sichuan.

The Indian-based Tibetan Center for Human Rights and Democracy and other activist groups Tuesday said at least 15 people were killed when police cracked down on Sunday's monk-led protests in Ngaba prefecture.

The Center and the exiled Tibetan government based in India have reported further pro-independence protests in Qinghai, Gansu and Sichuan Tuesday and the Tibet Autonomous Region. Reports of those incidents do not appear to have been published in Chinese media and Chinese authorities have not allowed foreign journalists to confirm details of the protests.

The exile government says at least 99 people have been killed in unrest over the past week, including 19 Tibetans who were shot dead by security forces Tuesday in new protests in Gansu province.

Witnesses in the Gansu county of Machu say police blocked off the streets after Buddhist monks and other Tibetans held a rally there. Witnesses told VOA's Tibetan service that they could confirm that at least 12 people were killed.

Chinese state media reports that the Tibetan capital Lhasa is returning to normal after riots that the government claims killed 13 people. The official Xinhua news agency says 105 people involved in Friday's riots have surrendered to police.

Foreign reporters asked Premier Wen Jiabao about the Tibetan protests during Tuesday's annual press conference. Mr. Wen repeated the government's claim that the Dalai Lama has orchestrated the protests, which the exiled Tibetan spiritual leader has denied.

China has controlled Tibet since 1951. The Dalai Lama and thousands of his followers fled from Tibet to India in 1959, during a failed revolt against Chinese rule. China denounces the Dalai Lama as a crusader for independence, but he says he has campaigned for nothing more than true autonomy for his homeland.