TOKYO - A strong earthquake with a preliminary magnitude of 6.3 has jolted in Tokyo and its environs.

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Japan's Meteorological Agency said the quake struck at 8:08 am local time (2308 GMT) Tuesday. The epicenter of the quake was located just off the coast of Chiba, east of Tokyo.

There were no initial reports of injuries or damage in the prefecture. No tsunami warning was issued.

The agency said the quake was a string of strong aftershocks since the 9.0-magnitute earthquake and ensuing tsunami in northeastern Japan on March 11. The twin disasters decimated much of the region, killing up to 25,000 people and setting off radiation leaks at a coastal nuclear plant by knocking out its cooling systems.