TOKYO -- The Japan Meteorological Agency said that tsunami waves at 30 cm high were observed in Ishinomaki city in Miyagi prefecture at about 3:07 am local time after a 7.1- magnitude quake hit off Fukushima prefecture in northeastern Japan early Saturday morning.

Waves at 20 cm high were also observed at Ofunato port in Iwate prefecture.

The agency has lifted all the tsunami warnings it issued earlier Saturday morning, saying "no tsunami damage is expected."

The Tokyo Electric Power Company said that no abnormalities had been detected at its crippled Fukushima Daiichi nuclear power plant after the quake, while the Tohoku Electric Power Company said no abnormality has been confirmed at its Onagawa nuclear power plant.

All but two of Japan's 50 reactors have been offline since a 9.0-magnitude earthquake and ensuing tsunami triggered multiple meltdowns and massive radiation leaks at the Fukushima Daiichi plant, about 250 kilometers northeast of Tokyo in March 2011.

Saturday's quake was registered at 4 on Japan's seismic scale of 7 in some parts in Tohoku area and strong tremor was felt in Tokyo, some 480 km away.

The epicenter, with a depth of 10 km, was initially detected at 37.2 degree of north latitude, 144.6 degree of east longitude, about 290 km east of Miyagi prefecture.