TOKYO -- An earthquake with a preliminary magnitude of 6.5 struck off the east coast of Japan's Kanto region to the southeast of the nation's capital Tokyo on Friday morning and may cause slight sea level changes in coastal regions, the Japan Meteorological Agency (JMA) said.

According to the weather agency here, the temblor occurred at 9:14 a.m. local time and struck at a latitude of 34.4 degrees north and longitude of 141.7 degrees east, with the epicenter in the Pacific Ocean some 150 km southeast of Katsuura, in southern Chiba Prefecture.

The weather agency registered the depth of the temblor as being 10 km under the sea.

On the Japanese seismic scale that peaks at 7, the quake measured 1 on the scale, the weather agency said, with Tokyo, neighboring Chiba and Kanagawa prefectures all within the seismic zone.

Nagano, Shizuoka, Gunma, Ibaraki, Fukushima, and Miyagi prefectures all saw the quake registered as 1 on Japan's seismic scale, according to the agency.

The weather agency has not issued a tsunami warning or advisory as a result of the off-shore quake, but said that while no damage had been reported as yet, there might be "slight sea-level changes in coastal regions."

The rise in quakes recently both in and in offshore regions of the landlocked Kanto area on the main island of Honshu, including Ibaraki Prefecture that borders the Pacific Ocean northeast of Tokyo and neighboring Saitama Prefecture, can be attributed to increased activity of late along the Japan Median Tectonic Line, the weather agency has said.

This fault system, also known as the Median Tectonic Line, is the longest in Japan and has seen increased activity lately, seismologists here have said.

The active fault system begins in Ibaraki Prefecture and also lies 3,000 meters beneath ground level in Saitama Prefecture, which borders the country's capital city of Tokyo.