The Nagasaki bombing occurred 68 years ago today, when the U.S. dropped an atomic bomb on the Japanese city of Nagasaki, which ultimately ended World War II. Survivors took a moment to remember this day in history, and to reflect on those lost.

A memorial service was held Friday, where survivors of the bombing joined Japan's prime minister. A bell in Nagasaki tolled at 11:02 a.m. local time, the exact time the bomb was dropped and reduced the city to rubble, WBIR reports via AP. About 6,000 people attended the memorial.

Those in Nagasaki paused for a moment of silence to remember the victims. The U.S dropped two atomic bombs on Japan during the final days of World War II.

The first hit Hiroshima on August 6th, 1945, which killed about 140,000 people, followed by the bombing of Nagasaki on August 9th, which killed about 70,000, according to VOA.

Nagasaki Mayor Tomihisa Taue criticized the Japanese government at the ceremony for refusing to sign a pledge rejecting the use of nuclear weapons under any circumstances. Mayor Tomihisa Taue said Japan's inaction "betrayed expectations of the global community," Fox News reports via AP.

The pledge was offered at an international disarmament meeting in April, VOA reports. Almost 80 countries signed the unconditional statement.

However, the document, prepared by a U.N. committee, was signed by countries which did not possess nuclear weapons. Countries such as the United States, Russia, India and Pakistan, which all possess nuclear weapons, also did not sign the pledge. Japan does not have any nuclear weapons.

Hiroshima held an observance of the first bombing on Tuesday. Prime Minister Shinzo Abe told a crowd of about 50,000 that Japan has a unique responsibility to push for the end of nuclear weapons.