Tsunami hits north-eastern Japan after massive quake
Japanese television showed cars, ships and even buildings being swept away by a vast wall of water after the 8.9-magnitude earthquake.
The quake has sparked fires in several areas including Tokyo, with at least 15 people reported dead.
It struck about 250 miles (400km) from the capital at a depth of 20 miles. There have been powerful aftershocks.
The tremor hit at 1446 local time (0546 GMT). Seismologists say it is one of the largest earthquakes to hit Japan for many years.
A tsunami warning was extended across the Pacific to include the Philippines, Indonesia, Taiwan, Hawaii, the Pacific coast of Russia and North and South America.
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.
Japan's NHK television showed a 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.
There 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.
Many people in Tokyo said they had never felt such a powerful earthquake.
In central Tokyo, Jeffrey Balanag said he was stuck in his office in the Shiodome Sumitomo building because the elevators had stopped working.
"There's no panic but we're almost seasick from the constant rolling of the building," he told the BBC.
Bullet train services to northern Japan were halted, rapid transit in Tokyo was suspended and some nuclear power plants automatically shut down.
Prime Minister Naoto Kan said there had been no radiation leaks.
In a televised address, he extended his sympathy to the victims of the disaster and said an emergency response headquarters had been set up.
Source: BBC