Police fired on hundreds of protesters in a Tibeten area of western China, killing eight people, an overseas activist group said. State media reported one government official was seriously injured in what it called a riot. Two monks also committed suicide late last month because of government oppression, another Tibetan activist group said Saturday. The reports indicate that unrest is continuing in China's Tibetan areas despite a massive security presence in place since violent anti-government demonstrations broke out in mid-March in Tibet's capital, Lhasa, and neighboring provinces. The London-based Free Tibet Campaign said Friday police fired on Buddhist monks and ordinary citizens who had marched on local government offices in Garze Tibetan Autonomous Prefecture in Sichuan province near Tibet on April 3. The protesters were demanding the release of two monks who were detained after 3,000 paramilitary troops searched their monastery and found photographs of the Dalai Lama, Tibet's exiled Buddhist leader, the group said. The U.S. government-funded Radio Free Asia said it had unconfirmed reports that up to 15 people were killed and dozens injured in the violence. Calls to local police and hospitals in the area were unanswered Saturday or else officials said they had no information. The official Xinhua News Agency had no information on deaths or injuries but confirmed that a riot broke out near government offices in Donggu town in Garze. An official was "attacked and seriously wounded," and police were "forced to fire warning shots and put down the violence," Xinhua said. On Saturday, the Tibetan Center for Human Rights and Democracy, based in India, said two monks committed suicide last month in Sichuan's Aba County following government oppression. Aba County has been the scene of large protests involving hundreds of monks and citizens. One monk, identified as Lobsang Jinpa, from the Aba Kirti Monastery killed himself March 27, leaving a signed note saying "I do not want to live under Chinese oppression even for a minute," the human rights group said. The second suicide occurred March 30 at the Aba Gomang Monastery, when a 75-year-old monk named Legtsok took his life, telling his followers he "can't beat the oppression anymore," the group said. It was impossible to verify the information since Chinese authorities have banned foreign reporters from traveling to the region. Also Saturday, state media reported more than 1 million people had signed an online Chinese petition alleging Western media bias in covering the Tibetan protests. The petition alleges that some Western media organizations, including CNN and BBC, have reported "untrue and distorted" stories on the Lhasa riots. Chinese authorities say 22 people died in anti-Beijing riots that broke out March 14 in Lhasa. The Tibetan government-in-exile says up to 140 were killed in the protests and ensuing crackdown. Beijing has accused Dalai Lama supporters of orchestrating the violence, a charge the spiritual leader has repeatedly denied. The protests are the longest and most sustained challenge to China's 57-year rule in the Himalayan region. China's subsequent crackdown has drawn international scrutiny and criticism in the run-up to this summer's Olympic Games.