Russia told North Korea on Monday to immediately return to the nuclear non-proliferation regime and resume talks with world powers, after the reclusive Communist state said it had conducted a nuclear test.
A Russian Foreign Ministry statement said the test was "fraught with danger for peace, security and stability in the region" but warned other countries against an over-hasty reaction.
"We demand that North Korea immediately undertakes steps to return to the nuclear non-proliferation regime and resume six-party talks," said the statement, posted on the ministry's official website www.mid.ru.
"The Russian Foreign Ministry urges all governments involved in the current difficult situation to show restraint and patience," it added.
Interfax news agency quoted an unnamed diplomatic source in Moscow as saying North Korea informed Russia two hours in advance about the test but this report could not immediately be confirmed.
Russia, along with the United States, China, South Korea and Japan, is involved in international efforts to persuade Pyongyang to abandon its nuclear weapons program.
Moscow has resisted Western calls to penalize North Korea for its nuclear ambitions. But last week Russia's foreign ministry described as "unacceptable" Pyongyang's plans to conduct a nuclear test.
Defense ministry spokesman Vyacheslav Sedov said in televised comments that Russia's system for monitoring nuclear tests had detected an nuclear explosion in North Korea at 0135 GMT.
"This was an underground test of a nuclear charge," he said.
Russian news agencies said North Korea's ambassador to Moscow had been summoned to the foreign ministry. The foreign ministry refused to comment on the report.
Interfax quoted an unnamed diplomatic source as saying Moscow was given advance warning of the test.
"The Russian ambassador in Pyongyang Andrei Karlov was summoned to the North Korean foreign ministry where he was handed a note about the forthcoming nuclear test," Interfaxsaid.
"The Russian ambassador was informed about the planned nuclear test two hours in advance," it added.
A U.S. official, speaking on condition of anonymity, said earlier on Monday that North Korea gave its key ally China only a 20-minute warning of the nuclear test
