China’s final preparations for the Olympics shifted into high gear on Monday with the launch of the official torch relay, amid rising anxiety and anger in Beijing that the high-profile event will be dogged by protests over Tibet and other issues.

Hu Jintao, the president, and Xi Jinping, his heir-apparent, presided over the ceremony in Tiananmen Square in central Beijing, seeing off the torch on the first leg of a journey that will take the symbolic flame around the world.