The last week's anti-Japan demonstrations in China have been a spectacular display of just how easily the ruling Communist Party can harness the power of protest. In the aftermath of nationwide protests, in which mobs trashed Japanese-owned businesses and set fire to Japanese model cars, critics are questioning the degree to which the Chinese government fanned the flames as part of its dispute with Japan over an island chain both nations claim.

"It is obvious that this was planned," said Ai Weiwei, the dissident artist, who videotaped some of the protests. The 1989 pro-democracy demonstrations in Tiananmen Square were "the last time that the people themselves organized a real protest and then the government sent in tanks to crush them," he said.

Although there has been no evidence that police officers participated in the violence, in many cities they directed the public on where to protest and cleared streets to allow tens of thousands to mass. Many protesters interviewed Tuesday, a traditional day of protest timed to the anniversary of the Japanese invasion of Manchuria in 1931, said they had been given the day off by employers to demonstrate.

"I need to lead the crowd and guide them to march in an orderly fashion," wrote a police officer in Jiangxi province in a microblog posting that was later removed.

Han Deqiang, a prominent Maoist professor, wrote that he demonstrated Tuesday in Beijing with 500 to 600 farmers who had come from Hebei province, which raised the possibility that buses had been organized for the demonstrations. ("The farmer brothers were holding Chairman Mao's portraits and they kept on chanting, 'Down with the Japanese Imperialists!'" he wrote.)