Japanese television has shown major tsunami damage in northern Japan today, following a magnitude-7.9 earthquake.

Public broadcaster NHK showed cars, trucks, houses and buildings being swept away by tsunami in Onahama city in Fukushima prefecture.

The earthquake struck off Japan's northeastern coast, shaking buildings in Tokyo for several minutes and prompting tsunami warnings.

Japan's meteorological agency warned that a tsunami as high as 20 feet (6 meters) could strike the coast near Miyagi prefecture, closest to the epicenter. Smaller tsunamis of up to 50 centimeters reached some coastal communities, the agency said.

The Pacific Tsunami Warning Center in Hawaii said a tsunami warning was in effect for Japan, Russia, Marcus Island and the Northern Marianas. A tsunami watch has been issued for Guam, Taiwan, the Philippines, Indonesia and U.S. state of Hawaii.

The quake struck at 2:46 p.m. at a depth of 10 kilometers, about 80 miles (125 kilometers) off the eastern coast, the meteorological agency said. The area is 240 miles (380 kilometers) northeast of Tokyo.

In downtown Tokyo, large buildings shook violently and workers poured into the street for safety. TV footage showed a large building on fire and bellowing smoke in the Odaiba district of Tokyo.

Footage on national broadcaster NHK from their Sendai office showed employees stumbling around and books and papers crashing from desks.

Police and coast guard officials said they were assessing possible damage from the quake.

Several quakes had hit the same region in recent days, including a 7.3 magnitude one on Wednesday.