* Moscow urges parties not to "cross the point of no return"

* Senior diplomat says war is unacceptable

* Moscow says U.S. statements are "a bit reassuring" (Adds diplomat's quotes)

SCOW, March 30 (Reuters) - Moscow urged restraint in the Korean peninsular on Saturday, after North Korea said it was entering a "state of war" with South Korea in a further escalation of its bellicose rhetoric against Seoul and its main ally, the United States.

"We hope that all parties will exercise maximum responsibility and restraint and no one will cross the point of no return," senior Russian Foreign Ministry official Grigory Logvinov told Interfax news agency.

North Korean leader Kim Jong-un on Friday put missile units on standby to attack U.S. military bases in the South and the Pacific, after two nuclear-capable U.S. stealth bombers flew over the Korean peninsula in a rare show of force.

"We expect that everyone understands that a recurrence of the war on the peninsula is definitely unacceptable," Logvinov told news agency RIA.

When asked by reporters if Pyongyang had the same understanding, Logvinov said: "Of course. We were in contact with the North Korean side".

U.S. officials said the B-2 bombers were on a diplomatic sortie aimed at reassuring allies South Korea and Japan and were also aimed at trying to nudge Pyongyang back to dialogue.

"At least at this point, we see that the statements (of Washington) are rather restrained. The position of the American side is a bit reassuring," Logvinov told RIA.

Russia warned on Friday that the heightened military activity was slipping into a "vicious cycle" that could get out of control.

Tension has been high since North Korea conducted a third nuclear weapons test in February in breach of U.N. sanctions and despite warnings from China for it not to do so.

As tensions rose close to Russia's eastern borders, President Vladimir Putin made staff changes within the Security Council, promoting Yuri Averyanov, with experience of Far East affairs, to the first deputy of the top security chief.

Averyanov moved to the Security Council in 2006 after six years as Putin's deputy representative for the Russian Far East. (Reporting by Maya Dyakina; Editing by Rosalind Russell)

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  • January 1951

    Six months after invading North Korean forces started the Korean War, North Korean leader and founder Kim Il Sung says in a speech that U.S. and South Korean forces were the actual invaders and had prompted his army to retaliate. Kim vows to annihilate the North's enemies. <em>Caption: In this March 7, 2013 photo released by the Korean Central News Agency (KCNA) and distributed March 8, 2013 by the Korea News Service, North Korean leader Kim Jong Un, center, uses binoculars to look at the South's territory from an observation post at the military unit on Jangjae islet, located in the southernmost part of the southwestern sector of North Korea's border with South Korea. (AP Photo/KCNA via KNS) </em>

  • January 1952

    Kim Il Sung likens U.S. forces to Nazis and says that the war is turning into a mass grave for U.S. forces. <em>Caption: In this March 7, 2013 photo released by the Korean Central News Agency (KCNA) and distributed March 8, 2013 by the Korea News Service, North Korean leader Kim Jong Un, center, walks with military personnel as he arrives for a military unit on Mu Islet, located in the southernmost part of the southwestern sector of North Korea's border with South Korea. (AP Photo/KCNA via KNS)</em>

  • May 1972

    Kim Il Sung tells Harrison Salisbury and John Lee of The New York Times that because of perceived U.S. hostility, "we are always making preparations for war. We do not conceal this matter." <em>Caption: North Koreans attend a rally in support of a statement given on Tuesday by a spokesman for the Supreme Command of the Korean People's Army vowing to cancel the 1953 cease-fire that ended the Korean War as well as boasting of the North's ownership of "lighter and smaller nukes" and its ability to execute "surgical strikes" meant to unify the divided Korean Peninsula, at Kim Il Sung Square in Pyongyang, North Korea, on Thursday, March 7, 2013. (AP Photo/Jon Chol Jin)</em>

  • March 1993

    North Korea declares a "semi-state of war" to protest joint U.S.-South Korean war games that it says threaten its security. Amid a standoff with Washington over its nuclear program, it also threatens to withdraw from the Nuclear Non-Proliferation Treaty. <em>Caption: In this Dec. 12, 2012 file photo released by Korean Central News Agency, North Korea's Unha-3 rocket lifts off from the Sohae launch pad in Tongchang-ri, North Korea. (AP Photo/KCNA, File)</em>

  • 1994

    In an appearance of what will become a well-worn phrase, a North Korean negotiator threatens to turn Seoul into "a sea of fire." Fearing war, South Koreans clear store shelves of instant noodles, water, gas and other necessities. <em>Caption: Female North Korean traffic police officers gather in front of bronze statues of the late leaders Kim Il Sung and Kim Jong Il to pay their respects in Pyongyang, North Korea on Saturday, Feb. 16, 2013. (AP Photo/David Guttenfelder)</em>

  • September 1996

    North Korea threatens "hundredfold and thousandfold retaliation" against South Korean troops who had captured or killed armed North Korean agents who had used a submarine to sneak into the South. <em>Caption: North Korean soldiers gather along a Pyongyang street during heavy snowfall on Sunday, Feb. 17, 2013. (AP Photo/David Guttenfelder)</em>

  • September 1996

    North Korea threatens "hundredfold and thousandfold retaliation" against South Korean troops who had captured or killed armed North Korean agents who had used a submarine to sneak into the South. <em>Caption: A North Korean soldier smokes a cigarette as snow falls in Pyongyang on Sunday, Feb. 17, 2013. (AP Photo/David Guttenfelder)</em>

  • January 2002

    After President George W. Bush labels North Korea part of an "axis of evil" with Iraq and Iran, Pyongyang calls the remark "little short of a declaration of war." North Korea's Foreign Ministry warns it "will never tolerate the U.S. reckless attempt to stifle the (North) by force of arms but mercilessly wipe out the aggressors." <em>Caption: A North Korean portrait photographer instructs North Korean soldiers to pose for a picture under a mosaic of the late leaders Kim Il Sung and Kim Jong Il at an exhibition in Pyongyang on Sunday, Feb. 17, 2013 where Kimjongilia flowers, named after Kim Jong Il, were on display. (AP Photo/David Guttenfelder)</em>

  • January 2010

    North Korea's powerful National Defense Commission warns that the country will initiate a "retaliatory holy war" against South Korea over Seoul's alleged contingency plan to deal with potential unrest in the North. <em>Caption: A North Korean man stands next to a tractor and wagon on the edge of a snow covered field near the village of Ryongsan-ri, south of Pyongyang, North Korea on Friday, Feb. 22, 2013. (AP Photo/David Guttenfelder)</em>

  • May 2010

    After a Seoul-led international investigation blames a North Korean torpedo for the sinking of a South Korea warship that killed 46 sailors, Pyongyang issues a denial and warns of a "prompt physical strike." In November 2010, the North attacked a front-line island, killing four South Koreans. <em>Caption: North Koreans cross a railroad bridge over a riverbed south of Mount Myohyang, and north of the capital city of Pyongyang, North Korea, Saturday, Feb. 23, 2013. (AP Photo/David Guttenfelder)</em>

  • November 2011

    A day after South Korea conducts large-scale military drills near the island hit by the North in 2010, the North's Korean People's Army threatens to turn Seoul's presidential palace into a "sea of fire." <em>Caption: In this Feb. 16, 2013 image made from video, North Korean leader Kim Jong Un, center, waves as he attends a statue unveiling ceremony at Mangyongdae Revolutionary School in Pyongyang, North Korea on the anniversary of late North Korean leader Kim Jong Il's birthday. (AP Photo/KRT via AP Video)</em>

  • April 2012

    North Korea holds a massive rally denouncing conservative South Korean President Lee Myung-bak as a "rat." It says he should be struck with a "retaliatory bolt of lightning" because of his confrontational approach toward Pyongyang. <em>Caption: Rows of North Korean children stand and salute at a sports arena in Pyongyang for a national meeting of the Children's Union on Saturday, Feb. 16, 2013. (AP Photo/Jon Chol Jin)</em>

  • June 2012

    North Korea's military warns that troops have aimed artillery at seven South Korean media groups to express outrage over criticism in Seoul of ongoing children's festivals in Pyongyang. It threatens a "merciless sacred war." <em>Caption: South Korean army soldiers patrol along the barbed-wire fence near the border village of Panmunjom, which has separated the two Koreas since the Korean War, in Paju, north of Seoul, South Korea, Saturday, Feb. 16, 2013. (AP Photo/Lee Jin-man)</em>

  • October 2012

    An unidentified spokesman at the powerful National Defense Commission warns that the U.S. mainland is within range of its missiles and says Washington's recent agreement to let Seoul possess missiles capable of hitting all of North Korea shows the allies are plotting to invade the North. <em>Caption: North Korean soldiers and others gather in front of bronze statues of the late leaders Kim Il Sung and Kim Jong Il to pay their respects in Pyongyang, North Korea on Saturday, Feb. 16, 2013. (AP Photo/David Guttenfelder)</em>

  • North Korean soldiers lay flowers at the base of bronze statues of the late leaders Kim Il Sung and Kim Jong Il to pay their respects in Pyongyang, North Korea on Saturday, Feb. 16, 2013. North Koreans turned out to commemorate what would have been the 71th birthday of Kim Jong Il who died on Dec. 17, 2011. (AP Photo/David Guttenfelder)