"We look back at the past only so that we don't repeat it in the future and that's incumbent on all of us", said Herbert Rothschild, planning committee chair.
More than 300,000 people across China were killed by Japan's biological weapons during WWII.
People mourn victims of the atomic bombings at the Peace Memorial Park in Hiroshima, Japan, on August 6, 2018.
Speaking at the ceremony, Abe said Japan will try to act as a bridge between nuclear powers and non-nuclear states and lead global efforts for a world without nuclear weapons.
At 8:15 a.m., the exact time when the US atomic bomb was dropped on Hiroshima on August 6, 1945, citizens including a representative of the bereaved families tolled a Peace Bell and participants offered a minute of silence.
Matsui also expressed hope for the easing of tensions on the Korean Peninsula to proceed through "peaceable dialogue", as the USA and North Korea reached an agreement to denuclearize the peninsula in their summit in June.
Expressing hope that the easing of tensions on the Korean Peninsula will continue through dialogue, Matsui called on global leaders to make an worldwide treaty comprehensively prohibiting nuclear weapons a "milestone" toward the goal of ridding the world of nuclear arsenals. It was the first use of nuclear weapons against human beings.
"Certain countries are blatantly proclaiming self-centered nationalism and modernizing their nuclear arsenals, rekindling tensions that had eased with the end of the Cold War", Matsui said Monday, without identifying the countries.
Among five major nuclear weapons states, representatives from the United States, France, Russia and Britain took part in the event.
The attack on Hiroshima, 700 kilometres west of Tokyo, in the closing days of World War II ushered in the nuclear age.
"Maintaining its three non-nuclear principles, our country is determined to make strenuous efforts to serve as a bridge between both parties", Abe said.
In Friday, Aug. 8, 2018, photo, Namio Matsura, 17-year-old member of the computation skill research club at Fukuyama Technical High School, watches Hiroshima city before atomic bomb fell in virtual reality experience at the high school in Hiroshima, western Japan.
Atomic bomb survivors and many visitors prayed for peace at the Peace Memorial Park near Ground Zero under the scorching summer heat.
Matsui's call however highlighted Japan's contradictory relationship with nuclear weapons although Japanese officials routinely argue that they oppose atomic weapons.
Speakers include Michael Vaughn, a military veteran; Denise Donnell of the Just Communities of Arkansas organization; Tristan Norman, a Hendrix College student-delegate who visited Japan earlier this year; and Frank LeBlanc, pastor of Westover Hills Presbyterian Church.
The bombs claimed the lives of 140,000 people in Hiroshima and 74,000 people in Nagasaki.