The raid on the press conference was the latest signal that Peking wants to stifle independent calls for compensation before next week's 50th-anniversary celebrations of the Japanese surrender in 1945, and during next month's United Nations World Conference on Women in Peking.
At the meeting Wang Aihua, 67, had tearfully begun to talk about her experiences as a "comfort woman", or sex slave, when the electricity to the hotel conference room was cut. A dozen uniformed and plainclothes policemen entered the room, stopped all filming and photography, confiscated videos and camera film, and took everyone's names.
Li Dingguo, one of the organisers, was taken away by police. Ms Wang, another former "comfort woman", other victims of Japanese war brutality and Tong Zeng, a campaigner for compensation, were allowed to leave. Reporters were told not to file reports.
China dropped official demands for compensation in 1972 when it established diplomatic ties with Japan, but it has previously said it would not stop private citizens seeking war reparations, and has voiced tacit support for them. But now, Peking appears to have toughened its stance against unofficial pressure groups.
The government has several concerns. It does not want to risk antagonising Japan, which is a big trade partner and the largest aid donor. It is equally reluctant to allow unofficial lobbyists to divert attention from the carefully scripted official anniversary celebrations on 15 August.
Nor can it risk being seen by a domestic audience to tolerate independent Chinese voices before the women's conference, when it is keen to keep strict control of Chinese participation.
Peking has banned Mr Tong from attending the Non-Governmental Organisation Forum held in parallel with the women's conference, where he was due to take part in a discussion on the Japanese army's use of "comfort women" during the war. On Sunday he appealed to the UN to intervene.
The authorities took away Mr Tong's passport 10 days ago to stop him going to Japan to present a lawsuit on behalf of 15 Chinese war victims, but the suit was filed in his absence yesterday in Tokyo. Other members of the group did receive passports and visas, and will travel to Japan to press their case.
The official propaganda in the run-up to 15 August has so far focused on detailing Japanese atrocities, and stressing the heroism of the People's Liberation Army in comparison to the Nationalist troops in the fight against the Japanese. China says it lost 35 million people at the hands of the Japanese, more than any other country.