A government panel said Tuesday that tsunami as high as 30 meters could hit Hokkaido in northern Japan and Iwate in the northeast if a magnitude 9 earthquake occurs along sea trenches off the country's Pacific coast.

The group of experts made the warning based on a worst-case scenario and said a mega-earthquake centered around the Japan Trench and the Kuril Trench off northern parts of the country could be "imminent."

While the Cabinet Office panel said it is difficult to calculate the probability such an earthquake could occur, it pointed to the fact that massive tsunami have happened in the region every 300 to 400 years with the latest observed in the 17th century.