Fifty years after the world's first atomic bomb detonated over Hiroshima, more than 1,000 people packed into a sweltering Washington National Cathedral last night to remember those who died in the blast and to call for the end of nuclear weapons.

"It is still painful to remember that day that so many, many were killed," Hiroshima survivor Hisayo Yamashita, 71, told the crowd. "It is the people who were killed that are asking for nuclear disarmament, and we must not waste their voices."

The hour-long ceremony included prayer and readings as well as traditional Japanese music. Members of religious and peace groups filled out the crowd, among them actor and activist Martin Sheen and longtime antinuclear demonstrator Daniel Berrigan.

"These are prayers for all those who have suffered from nuclear weapons. We feel on this 50th year, it's a time we can remember what happened in Hiroshima and Nagasaki and commit ourselves so it doesn't happen again," said Tricia Sullivan, coordinator for Pax Christi, a peace group that helped organize the gathering. "It's painful for people to think about. It's easier to forget and let it pass."

Some in the crowd, such as Margaret Dear, of Potomac, said they long have been haunted by the bomb's devastation.

"How could I not come out to this?" asked Dear, a mother of one of the event's organizers who was 13 when the bombing took place. "Trying to figure out what America and what Japan did wrong is beyond us right now. But we can be prayerful. It all comes down to prayer, remembrance and to try to see a better future."

On Aug. 6, 1945, a B-29 Superfortress bomber named the Enola Gay dropped an atomic bomb on the Japanese city of Hiroshima. Three days later, a second bomb exploded over Nagasaki, setting the stage for Japan's surrender. At least 100,000 died from the bombings.

Around the area, several Sunday church services wove the Hiroshima bombing's anniversary into their programs.

At the Cathedral's morning service, the Rev. Alan Geyer's sermon before nearly 700 people questioned the morality of the bombings.

"Men, women and children were killed for the sake of victory and peace," said Geyer, adding that Christians should "feel the deepest sorrow for what happened August 6, 1945."

At noon, about a dozen protesters from the environmental group Greenpeace picketed the Smithsonian Institution's Air and Space Museum, where part of the Enola Gay is on display, with signs reading "No more Hiroshima's" and "Never again."

Among the hundreds of tourists watching the protesters was Lewis Hogan of Butler, Pa., who was 13 when the United States dropped the bombs.

"Those bombs shortened the war. . . . Anything that shortened the war was a good thing," Hogan said.

Nearby, Patrick Triano, who lives in the District, knelt on the ground in front of the protesters and balanced his 5-year-old son, Tarig, on his lap.

"What is Hiroshima?" Tarig asked.

"It's a city. Hiroshima and Nagasaki were where they first dropped the atomic bombs on people," his father responded.

"This is part of his history," Triano said, adding that he believes it was wrong to have dropped the bombs. "I want him to know what happened then, what's happening now and why these people are doing what they're doing."