MOSCOW (Reuters) - Russia is taking security measures as a precaution against the possibility tension over North Korea could escalate into nuclear war, news agencies quoted officials as saying on Wednesday. Russia also summoned North Koreas Ambassador and called for a return to six-party nuclear disarmament talks, the Russian Foreign Ministry said. Interfax quoted an unnamed security source as saying a standoff triggered by Pyongyangs nuclear test on Monday could affect the security of Russias far eastern regions, which border North Korea. The need has emerged for an appropriate package of precautionary measures, the source said. We are not talking about stepping up military efforts but rather about measures in case a military conflict, perhaps with the use of nuclear weapons, flares up on the Korean Peninsula, he added. The official did not elaborate further. Itar-Tass news agency quoted a Russian Foreign Ministry official as saying the war of nerves over North Korea should not be allowed to grow into a military conflict, a reference to Pyongyangs decision to drop out of the armistice deal. We assume that a dangerous brinkmanship, a war of nerves, is under way, but it will not grow into a hot war, the official told Tass. Restraint is needed. Russian President Dmitry Medvedev has condemned the North Korean tests but his Foreign Minister, Sergei Lavrov, has warned the international community against hasty decisions. Medvedev told South Korean President Lee Myung-bak, who called him on Wednesday, that Russia was prepared to work with Seoul on a new UN Security Council resolution and to revive international talks on the North Korean nuclear issue. The heads of state noted that the nuclear test conducted by North Korea on Monday is a direct violation of a UN Security Council resolution and impedes international law, a Kremlin Press release said. In a statement, the Foreign Ministry said the Russian side called for a renewal of six-party talks on the denuclearisation of the Korean peninsula with the goal of finding a political-diplomatic solution to the regions security problems. Meanwhile, US Secretary of State Hillary Clinton on Wednesday underscored the US commitment to defend South Korea and Japan amid threats from North Korea. I want to underscore the commitments the United States has and intends always to honour for the defence of South Korea and Japan, Hillary told reporters in Washington. The White House meanwhile, said the US views N Koreas recent threats as sabre-rattling and bluster that will only deepen the countrys isolation from the world. Were certainly concerned and take any threat seriously. But my sense is theyre trying to get renewed attention through sabre-rattling and bluster and threats, said spokesman Robert Gibbs. And threats wont get North Korea the attention it craves. Their actions are continuing to further deepen their own isolation, from the international community, Gibbs told reporters.