Former Hiroshima Mayor Tadatoshi Akiba on Thursday urged Russian President Vladimir Putin not to use nuclear weapons in Ukraine after the Russian leader put his nuclear forces on high alert following his launch of an invasion of the country last month.

Akiba, who started a petition earlier this month demanding Putin and world leaders declare they will not use nuclear weapons in the Ukraine crisis, said at a news conference Putin's move has left atomic bomb survivors and many other people appalled.

He said the victims of the 1945 U.S. atomic bombings on Hiroshima and Nagasaki went through a "living hell" and "despicable reality they somehow managed to survive," and urged leaders of nuclear states to visit the two cities to learn about the damage a nuclear attack can bring.

The former mayor requested Japanese Prime Minister Fumio Kishida to meet Putin and other heads of nuclear weapons states to "convey the convictions of hibakusha," as atomic bomb survivors are called in Japan, seeking the abolition of nuclear weapons.

The premier, elected from a Hiroshima constituency, has the "power to persuade" them, Akiba said at the Foreign Correspondents' Club of Japan in Tokyo.

Since the start of its invasion on Feb. 24, Russia has targeted several nuclear facilities in Ukraine, raising fears of a nuclear catastrophe.

The petition Akiba started on March 1 has so far gathered over 92,000 signatures, against its target of 150,000.

He warned against former Japanese Prime Minister Shinzo Abe's recent suggestion that Tokyo should start discussions about the possibility of a nuclear weapon sharing arrangement with Washington, saying such a move would provoke Japan's neighbors and could result in a war.

Such "conflict-causing rhetoric should not be lightly expressed, especially from a former prime minister," he added.

Meanwhile, a group of local mayors in Japan called on the Russian military to cease attacks on Ukraine's nuclear power plants in an emergency statement Thursday, saying they threatened to "spread nuclear contamination on a wide scale, exposing people in Russia and many other countries to radiation."

The Mayors for a Nuclear Power Free Japan also demanded Moscow withdraw its troops from Ukraine. The group was formed in 2012, a year after the Fukushima nuclear crisis, triggered by a quake-caused tsunami, to promote a shift in Japan's policy to renewable energy.

Earlier in the month, Moscow shelled a nuclear research institute in Kharkiv, eastern Ukraine, after attacking the Zaporizhzhya Nuclear Power Plant -- Europe's largest nuclear power station, located in the southern part of the country. Russia also captured the Chernobyl nuclear power complex in the north.