Russia has criticised North Korea after it announced it was withdrawing from international disarmament talks, saying it had made the "wrong choice".
North Korea's announcement has attracted international criticism
Pyongyang also said for the first time on Thursday that it had nuclear arms.
It said it needed the weapons as protection against what it considered an increasingly hostile United States.
Meanwhile North Korean state media called on its citizens to show "single-minded unity" and "devotedly protect" their leader, Kim Jong Il.
"If the information proves accurate, I would say North Korea has made a wrong choice," Russian Defence Minister Sergei Ivanov said at a security conference in Munich on Saturday.
"And we have to remember that this state is sharing a common border with Russia."
Since 2003, Russia has been involved six-party negotiations with the US, China, South Korea and Japan to persuade North Korea to abandon its nuclear weapons programme.
Mr Ivanov also rejected North Korea's push for bilateral talks with the US.
He said: "We should do all we can to keep that state in the (nuclear non-proliferation) treaty framework and for that purpose, compromise solutions will be required ... within the ongoing six party talks."