North Korea's mobile missile launcher, carrying a ballistic missile, has been seen moving near the east coast and activity has also been seen at a long-range rocket launch pad on the west coast, Japanese public broadcaster NHK said on Thursday.

International pressure has grown on North Korea to call off a planned rocket launch, seen by some governments as another missile test, since Pyongyang told U.N. agencies this week it would launch what it called an "earth observation satellite".

Japan has put its military on alert to shoot down any rocket that threatens its territory.

The NHK report said the mobile missile launcher was thought to normally remain stationary in places such as an underground facility.

North Korea fired two mid-range ballistic missiles, which appeared to be Rodong-class missiles, from the mobile launcher off its east coast into the sea towards Japan in March 2014, the report said.