Russia is urging North Korea to cancel its plan to launch a rocket later this month.
The Russian Foreign Ministry said in a statement on December 3 that a launch would be in violation of UN resolutions.
Pyongyang says the rocket will carry a satellite into orbit.
Many view it as a disguised test for an intercontinental ballistic missile that could carry nuclear warheads.
North Korea carried out two nuclear weapons tests in 2006 and 2009.
North Korea's plan has already been condemned by the United States. China -- the communist North's main ally -- has expressed "concern."
South Korea and Japan said they were considering a response.
Japanese government spokesman Osamura Fujimura cautioned the North on December 3.
North Korea says it will send a long-range rocket into space between December 10 and 22. It would be North Korea's second launch this year after a failed attempt in April.
South Korea's Yonhap news agency, citing a government source in Seoul, reported on December 3 that the first stage of the rocket has already been placed in position at the North's Sohae satellite launch station.
The Japanese government spokesman said all precautions will be taken to ensure people's safety.
"If, in fact, North Korea should launch the rocket, we plan to make all the necessary information available through the national emergency warning system, and we ask that all listeners pay attention to all radio and TV news as well," Fujimura said.
Japan has reportedly started to deploy missile interceptors in Okinawa. Media reports said the military has ordered the rocket destroyed if it enters Japanese airspace.
The North's last rocket launch, in April, ended in failure with the carrier flying just over two minutes before breaking up and falling into the Yellow Sea.
The United States, China, Russia, Japan, and South Korea are all involved in the stalled six-party talks with North Korea on its nuclear weapons program.
With reporting by Reuters and ITAR-TASS