An earthquake with a preliminary magnitude of 5.5 struck early Thursday off the Ogasawara Islands, about 1,000 kilometers south of Tokyo, the weather agency said.

The 12:21 a.m. quake, which originated at a depth of about 10 kilometers, registered 4 on Japan's seismic intensity scale of 7 in Hahajima Island, one of the two inhabited islands in the chain, the Japan Meteorological Agency said, adding that the temblor did not cause a tsunami.

An intensity of 4 means that most people are startled and would be woken up from sleep by the quake.