A series of strong earthquakes including one with a magnitude of 6.7 hit the Tokyo area early Thursday, cutting off power to more than 2,000 homes and causing light injuries, officials and reports said.

Japan's meteorological agency warned that more moderate aftershocks could strike, although there were no fears of a tsunami.

The strongest earthquake hit at 1:45 am (1645 GMT) in the Pacific Ocean off Ibaraki prefecture, some 100 kilometres (60 miles) northeast of Tokyo.

Public broadcaster NHK said that two people were lightly injured, including an 18-year-old boy who was hit by his falling stereo speaker.

Power was cut off to 2,100 households, the network said, quoting local officials.

The impact was strongest in Ibaraki and adjacent Tochigi prefecture where the earthquake measured lower-five on the seven-point Japanese scale -- strong enough to crack holes in weak buildings.

"We felt a strong jolt, but there are no reports as of now of any major damage," an Ibaraki police spokesman said.

Highway operators said they had lowered the speed limit as a precaution, although they had not detected any damage to the roads from the quake, which struck at a depth of 40 kilometres (25 miles).

The earthquake followed a series of tremors off the Pacific coast early Thursday, including one measuring 6.3 on the Richter scale.

The quakes rattled buildings in the heart of Tokyo, where Chinese President Hu Jintao was staying on a rare visit to Japan.

Japan experiences 20 percent of the world's major earthquakes and has developed an infrastructure meant to withstand violent tremors.

A 6.8-magnitude earthquake rocked central Japan in July last year, killing 11 people and shutting down the world's largest nuclear power plant.

Tokyo Electric Power Co. said its nuclear power plants were not damaged by the latest earthquakes, according to NHK.

Japan lies at the crossing of four tectonic plates and is constantly bracing for the dreaded "Big One" feared to inflict major damage.

A 7.3-magnitude earthquake in Tokyo could kill 4,700 people, damage 440,000 buildings and leave thousands of others trapped in elevators, according to a study published by the government in 2006.

The last major tremor in Tokyo was the Great Kanto Earthquake of 1923 which left 142,807 people dead or unaccounted for. Japan marks the September 1 anniversary each year with nationwide disaster preparation drills.