The quake hit the Noto peninsula on the west coast of Japan's main island of Honshu at 4:33 am (1933 GMT) at a depth of 11 kilometers (seven miles), the agency said, adding there were no reports of casualties and no risk of a tsunami.

Smaller aftershocks with magnitudes of 3.1 and 2.9 followed.

A spokesman for the agency said the tremors were aftershocks to a 6.9-magnitude earthquake that rocked the region on March 25, 2007, leaving one dead and hundreds wounded.

"Although nearly a year has passed since that earthquake it is still possible the region will experience further aftershocks although on a smaller scale," he said. The area is some 300 kilometers northwest of Tokyo.

The 2007 quake reduced hundreds of homes rubble and forced thousands of residents to take cover in emergency shelters.

"For a second I thought it was like last year's earthquake and it really startled me," a local resident told private broadcaster TBS.

A local official said no damage had been reported.

Japan experiences about 20 percent of the world's major earthquakes.