HIROSHIMA, Aug. 4 Kyodo -- The Japan Congress Against A and H Bombs (Gensuikin) opened a three-day conference Sunday evening in Hiroshima with some 4,000 people participating.

At the outset of the meeting, participants offered a silent prayer for victims of the atomic bombing of the city by the United States in 1945.

Shigetoshi Iwamatsu, chairman of the meeting's executive committee, stressed that Gensuikin aims not only for the abolition of nuclear weapons but also for the scrapping of nuclear power stations in the country.

Kevin Martin, an American peace activist and one of nine overseas guests at the conference, gave a brief speech denouncing U.S. policy under President George W. Bush.

''The United States, unfortunately, still plans to commit more atrocities like Hiroshima and Nagasaki as we are preparing to build and test and develop new types of nuclear weapon even to use them on nonnuclear states,'' he said.

One of three high school students who made an appeal for peace at the event said, ''When I heard from a survivor of the atomic bombing about his experience, I thought he was exaggerating.''

''But as I continued to listen how the atomic bomb slowly descended from the sky attached to three parachutes, I felt scared,'' he said.

Prior to the meeting, eight of the overseas guests visited the Hiroshima Peace Memorial Museum in Naka Ward.

One of the eight, Mohamed Bendjebbar, is a former Algerian military officer who was involved in the management of former French nuclear test sites in the Sahara Desert after French forces withdrew in 1967 and later suffered deteriorated health.

Bendjebbar said, ''We human beings must conserve this kind of museum so that we will not repeat the same mistake.''

The Algerian said he saw in the late 1950s a former Nazi concentration camp for Jews and described the A-bomb attack on Hiroshima as the same kind of human error.

Gensuikin is backed by the main opposition Democratic Party of Japan, the Social Democratic Party and the Japanese Trade Union Confederation (Rengo), Japan's largest labor group.

Meanwhile, the Japan Council Against A and H Bombs (Gensuikyo), a rival group, wrapped up its international conference earlier in the day in Hiroshima by adopting a declaration calling on all nuclear powers to renounce a nuclear first-strike policy.

''We demand that the nuclear weapons states that have not yet renounced the nuclear first-strike policy should do so immediately and that they should pledge not to use their nuclear weapons,'' the declaration said.

The declaration denounced the U.S., saying, ''In defiance of the voices calling for the abolition of nuclear weapons, the U.S. government is preparing scenarios to launch nuclear first strikes in pursuit of its hegemonic objectives.''