Tokyo, June 28 : An earthquake with a preliminary magnitude of 6.1 struck off Iwate Prefecture in northeastern Japan early Sunday, the country's weather agency said. No tsunami warning was issued.

The temblor occurred at 5:21 a.m. local time off Iwate's eastern coast at a depth of about 40 km, measuring lower 5 on Japan's seismic intensity scale of 7 in parts of Aomori and Iwate prefectures, reports Xinhua, quoting the Japan Meteorological Agency.

No abnormalities were reported at the Higashidori nuclear power plant in Aomori or at the Onagawa nuclear power complex in Miyagi Prefecture, according to their operator.

The quake's epicentre was located at a latitude of 40.2 degrees north and a longitude of 142.4 degrees east.

A 7.2-magnitude earthquake jolted the same region on Thursday, injuring at least 10 people.

Friday saw two quakes -- a 5.6-magnitude and 5.8-magnitude -- strike near Tokyo, with shaking clearly felt in the capital. At least 10 people were injured.

At 11:49 a.m. on Friday, a 4.1-magnitude earthquake hit southern Ibaraki Prefecture, with tremors also clearly felt in the capital.

Meanwhile, on Thursday, at least four people were injured after a 7.2-magnitude earthquake struck northeastern Japan.

The temblor, revised up from a preliminary magnitude of 6.9, occurred at around 7:30 a.m. local time off the eastern coast of Iwate Prefecture at a depth of about 40 km. It measured upper 6, the second-highest level on Japan's seismic scale of 7, in Hashikami Town and lower 6 in Hachinohe City, both in Aomori Prefecture, the Japan Meteorological Agency (JMA) said.

An intensity of lower 6 means it is difficult to remain standing, and unsecured objects like furniture may topple over, and windows may be damaged, reports Kyodo News, quoting the agency.

/IANS