TOKYO —  A strong earthquake with a preliminary 6.6 magnitude struck off of Japan's eastern coast Saturday, the country's meteorological agency said. There were no immediate reports of injuries or damage.

The 11:39 a.m. quake, which occurred off the coast of Fukushima prefecture about 150 miles northeast of Tokyo, was followed by several aftershocks.

The quake, which struck about six miles below the ocean's surface, shook buildings as far away as Tokyo.

The agency issued a tsunami warning for parts of Japan's eastern coast, but the Pacific Tsunami Warning Center in Honolulu said there was no broad threat in the Pacific.

However, earthquakes of this magnitude can generate local tsunamis that can be destructive within a 60-mile range, the tsunami center said.

"There are no reports of damage, but tsunamis are still a threat and so we have evacuated the beaches. There were a lot of people out because the weather was so nice today," said Toshihiko Keiokawa, a policeman near where the quake hit.

He had no immediate estimate on the number of evacuees.

Surfers were brought in to land in neighboring Miyagi Prefecture, where there were also no reports of damage or injury, said Norio Watanabe, a local police spokesman.

Japan sits atop four tectonic plates and is one of the world's most earthquake-prone countries.

Last month a 7.2-magnitude earthquake struck sparsely populated rural areas in northern Japan, killing at least 12 people, leaving 10 others missing and injuring more than 300.