MOSCOW, October 10 (RIA Novosti) - North Korea has become the ninth nuclear power de facto, Russia's defense minister said Tuesday.

The reclusive Communist state announced Monday that it successfully detonated a nuclear device underground, in defiance of a UN Security Council statement urging it to give up its nuclear test plans and return to disarmament talks, and earlier warnings from the international community.

"North Korea has turned into the ninth nuclear power," Sergei Ivanov, who is also deputy prime minister, told journalists, adding that North Korea's nuclear test is a serious blow to the nuclear non-proliferation regime,

"Such events arouse justifiable fear and indignation," he said.

He said Russian experts have no doubt that the explosion was a nuclear one, but refused to give details.

"We have our secret methods, but I will not discuss them," he said

The minister said no dangerous substances in the atmosphere have yet been detected following North Korea's nuclear test.

"No traces of substances harmful to humans have been detected in the atmosphere," he said.

Ivanov said that Russian experts made a precise evaluation of the nuclear explosion's strength, without specifying the figure.

The Russian Defense Ministry put the figure at 5-15 kilotons of TNT equivalent Monday, while initial U.S. estimates were substantially lower.