Tokyo — A powerful earthquake struck off the northern Japanese coast Monday, prompting the Japan Meteorological Agency (JMA) to issue a tsunami alert in the region.

The quake registering a preliminary magnitude of 7.5 occurred off the coast of Sanriku in northern Japan at around 4:53 p.m. (2:53 a.m. Eastern on Sunday), at a depth of about 6 miles below the sea surface, the agency said.

The JMA reported the first tsunami waves, about three feet high, hitting a port in Kuji, in the northern Iwate Prefecture. 

In a press release, the agency warned that a bigger tsunami could hit after the first waves.

"Tsunamis can strike repeatedly. Do not leave your safe place until the warning is lifted," they wrote.

Officials also advised people to move to higher ground and look out for landslides or other earthquakes later in the week.

Japan's NHK public television said earlier that tsunami waves up to 10 feet high could hit the area shortly, and there were warnings for residents along the eastern coasts of Iwate, on Japan's main island of Honshu, and on the northern island of Hokkaido, to evacuate inland to higher ground.

Prime Minister Sanae Takaichi told reporters in Tokyo that the government had established an emergency task force, and television screens flashed warnings for people in Iwate, Aomori and Hokkaido to evacuate. 

"Residents in areas under tsunami warnings should immediately evacuate to higher ground or safe elevated locations," she said.

National public broadcaster NHK showed video of ships heading out of a port in Hokkaido in anticipation of the waves, and Japan's Kyodo news agency said high-speed bullet train services in Aomori were suspended.

It has been 15 years since a magnitude 9.0 earthquake struck, unleashing a massive tsunami on March 11, 2011, ravaging parts of northern Japan. More than 22,000 people were killed and nearly half a million people were forced to flee their homes, most of them due to tsunami damage.

Some 160,000 people fled their homes in the Fukushima Prefecture because of the radiation spewed from the tsunami-hit Fukushima Daiichi nuclear power plant. About 26,000 of them haven't returned because they resettled elsewhere, their hometowns remain off-limits or they have lingering concerns about radiation.

There were initial reports in Japanese media that at least two nuclear power plants in the northeast region under a tsunami warning on Monday were thus far unaffected by the earthquake. Both of the plants are currently offline.

It was the tsunami that came after the 2011 temblor that caused most of the damage at the Fukushima Daiichi plant, however.