A powerful earthquake with a preliminary magnitude of 6.9 rattled Japan's southern islands early Saturday, injuring two and initially prompting fears of a tsunami.

There were no reports of serious damage from the quake, believed to be the strongest in a century to hit Japan's southern Okinawa Island. Japan's Kyodo news agency said two people were hurt, but there were no reports of any deaths.

The quake occurred off the coast of the island of Okinawa at a depth of 6.2 miles at 5:31 a.m. Saturday, the Meteorological Agency said.

The only damage reported hours after the quake was ruptured water pipes in two locations, Okinawa police official Noritomi Kikuzato said.

The Meteorological Agency had initially predicted a tsunami up to 6 feet near the Okinawan coast and warned nearby residents to stay away from the coastline. The agency lifted the warning within two hours after observing only a small swelling of the tide.

"I was fast asleep when the quake hit, and I jumped out of bed. It felt like the shaking lasted forever," Ryota Ueno, a town official in the Nishihara district of Okinawa, told public broadcaster NHK.

Masaaki Nakasone, an official in Nanjo town, said his house shook violently but all furniture and other objects stayed intact.

"First there was a vertical shaking, then the house swayed sideways," Nakasone said.

Okinawa is about 1,000 miles southwest of Tokyo.

The quake registered a 5 on the Japanese scale, which measures intensity in specific locations and goes up to 7. Kyodo said that made it the strongest to hit the island since 1909.

Japan is one of the world's most earthquake-prone countries. In 1995, a magnitude-7.2 quake in the western port city of Kobe killed 6,400 people.