The government's earthquake research panel on Tuesday warned of a possibly "impending" magnitude 9 class quake in the Pacific off the eastern coast of Hokkaido that would likely trigger a massive tsunami.

A huge earthquake occurred about 400 years ago off eastern Hokkaido, an area that has seen large temblors in a cycle of every 340 to 380 years. The last mega-quake caused tsunami over 20 meters high and flooded about 4 kilometers inland from the coast, according to research by Hokkaido University.

The chances are high that another large earthquake is "impending" in the area, the panel said in a long-term quake projection report released Tuesday.