TOKYO (Kyodo) -- Tokyo on Monday marked the 80th anniversary of a night of U.S. air raids during World War II that killed around 100,000 people amid concern over fading memories of the devastating bombing.

A memorial service was held at a park facility in the capital's Sumida Ward that houses the remains of many of the victims. With over 87 percent of Japan's population born after the war, participants pledged to pass on memories to future generations.

"We must keep the memories and lessons of this horrific war in our hearts and pass them on to future generations," Japanese Prime Minister Shigeru Ishiba said in a message to the event, which was joined by some 160 people including families of the victims.

Tokyo Gov. Yuriko Koike as well as Crown Prince Fumihito and Crown Princess Kiko attended the ceremony.

"The victims and their families have worked tirelessly to build the Tokyo of today. With this in mind, we will pass on a sustainable city to the future," Koike said.

In the early hours of the morning on March 10, 1945, U.S. B-29 bombers dropped incendiary bombs on parts of Tokyo, particularly on densely populated areas, burning down an estimated 270,000 residential buildings overnight.

Many people failed to escape due partly to a law prohibiting evacuation during air raids and obliging people to extinguish fires. While some 100,000 people are said to have died, the exact figure remains unclear.

"Had I not evacuated earlier to (neighboring) Chiba Prefecture, I would have died too," said a 90-year-old woman who lost four family members including her younger brother in the bombing.

"I will never forget how my brother saw me off as I left," she said in tears.

The Japanese government has not compensated civilian victims of the war in the belief that the people should equally endure damage caused by a war emergency, prompting their families to seek damages from the state.

A bipartisan group of lawmakers is seeking to submit a bill during the current Diet session to compensate some civilian victims.

After the March 10 raids, the United States attacked other cities and towns across Japan, and dropped atomic bombs on Hiroshima on Aug. 6 and on Nagasaki on Aug. 9, 1945. The war ended Aug. 15 that year.