People in Hiroshima are protesting the latest nuclear test by the United States. The US government announced last week that the country carried out a subcritical nuclear test earlier this year.
A US government laboratory said it carried out the experiment in Nevada in February as part of a drive to modernize the country's nuclear weapons.
It was the first test of its kind since December 2017, and the second under the current administration.
A subcritical test does not produce a large nuclear explosion.
People in Hiroshima are protesting the move. About 80 people from 12 groups, including survivors of the 1945 atomic bombing of the city, took part in a 20-minute protest on Monday. The sit-in was held at the cenotaph for bomb victims in the city's Peace Memorial Park.
Toshiyuki Mimaki, a representative of an atomic bomb survivors' group said, "The world is only halfway along the path to doing away with nuclear arsenals, despite progress such as the adoption of the Treaty on the Prohibition of Nuclear Weapons at the UN."
Protest participants plan to collect signatures and send letters expressing displeasure to US President Donald Trump via the US embassy.
City officials also showed their indignation.
Hiroshima Mayor Kazumi Matsui said, "The subcritical test is an unforgivable act that tramples on the feelings of atomic bomb survivors wishing for a world without nuclear weapons."
The governor of Hiroshima prefecture Hidehiko Yuzaki sent a letter of protest to the US president urging him to halt all kinds of nuclear testing. The missive also urges the US leader to visit Hiroshima to gain an understanding of the extent of the destruction caused by the atomic bomb.
Japan's Chief Cabinet Secretary said the experiment did not violate a UN nuclear test ban treaty. Yoshihide Suga told reporters that subcritical tests should be discussed as part of the effort to achieve global nuclear disarmament.