Obama arrived at Hiroshima's atomic bomb park Friday on the first visit by a sitting US president and was greeted by Japanese Prime Minister Shinzo Abe.
“You’re not welcome here” and “Get out of Hiroshima,” the protesters shouted in a rally held at the Hiroshima Peace Memorial Park, Press TV reported.
They held banners that read, “Get rid of all nukes immediately,” “Remove all US bases from Okinawa” and “We won’t let you use military alliances to start your next war.”
Among the protesters, there were labor union members, college students as well as survivors and the relatives of the victims of the Hiroshima bombing on August 6, 1945.
Obama has said he will not apologize for the bombing, which killed thousands instantly, and some 140,000 by that year’s end.
“I want Obama to say ‘I’m sorry.’ If he does, maybe my suffering will ease,” said 73-year-old Eiji Hattori, who was a toddler at the time of the bombing and now has three types of cancer.
“If Obama apologized, I could die and meet my parents in heaven in peace,” he said.
Obama's visit to Hiroshima has stirred heated debate, with critics pointing to paradoxes in policies relying on nuclear deterrence while calling for an end to atomic arms.
The city of Nagasaki was hit by a second nuclear bomb on Aug. 9, 1945, and Japan surrendered six days later.
The US justifies the bombings, contending that they were necessary to end the war and save lives, although many historians question that view and believe they were unjustified.
Aides say Obama's main objective in Hiroshima is to showcase his nuclear disarmament agenda. However, critics say he has made scant progress and is spending heavily to modernize the US atomic arsenal.
Japan, despite advocating disarmament, relies on the US nuclear umbrella for extended deterrence.
Among the governments critical of the visit, North Korea on Friday denounced Obama’s visit to Hiroshima as an act of stunning hypocrisy and "a childish political calculation."
“Even if Obama visits the damaged city, he cannot hide his identity as a nuclear war fanatic and nuclear weapons proliferator,” read part of a report on North Korea’s official Korean Central News Agency (KCNA).