The two mayors of the Japanese cities that suffered US atomic bombing in World War II condemned the United States on Friday for conducting a subcritical nuclear test at a Nevada test site Wednesday.

Hiroshima Mayor Kazumi Matsui and Nagasaki Mayor Tomihisa Taue sent letters of protest to US President Barack Obama separately.

Matsui said the US action ignored the wish of the atomic bombing survivors and millions of others who seek the abolition of nuclear weapons and was utterly unacceptable.

"On behalf of the A-bombed city of Hiroshima, I vehemently protest," he added.

Taue said that the nuclear test by the US goes counter to the movement in the international community to abolish nuclear weapons. He urged Obama to engage sincerely in nuclear arms reduction and to play leading role in the effort to bring about "a world without nuclear weapons" as early as possible.

Meanwhile, A-bomb survivors in Hiroshima and Nagasaki also denounced the US nuclear test.

Koichi Kawano, 72, who heads a council of the Nagasaki Peace Action Center, was quoted by Kyodo News as saying that he hoped President Barack Obama would strive for a nuclear-free world in his second four-year term. He urged the Japanese government to file a strong protest with Washington over the subcritical nuclear test.

The United States conducted a subcritical nuclear test Wednesday at a Nevada underground test site, the first in about 22 months. It was the fourth confirmed subcritical nuclear test under the administration of President Obama.