Strong waves hit Japan's Miyagi and Fukushima prefectures, officials said, damaging dozens of coastal communities. Kyodo news agency said a 10-metre wave (33ft) struck the port of Sendai in Miyagi prefecture.
massive surge of debris-filled water sweeping away buildings, cars and ships and reaching far inland.
Motorists could be seen trying to speed away from the wall of water.
Farmland around Sendai was submerged and the waves pushed cars across the runway of the city's airport.
Kyodo said at least 15 people had been killed in the earthquake and tsunami. It was believed the death toll could rise significantly.
The earthquake also triggered a number of fires, including one at an oil refinery in Ichihara city in Chiba prefecture near Tokyo, engulfing storage tanks.
here were reports of about 20 people injured in Tokyo after the roof of a hall collapsed on to a graduation ceremony.
Residents and workers in Tokyo rushed out of apartment buildings and office blocks and gathered in parks and open spaces as aftershocks continued to hit.
In central Tokyo, Jeffrey Balanag said he was stuck in his office in the Shiodome Sumitomo building because the elevators had stopped working.
Bullet train services to northern Japan were halted, rapid transit in Tokyo was suspended and some nuclear power plants automatically shut down.