The quake struck at around 8:29 am (2329 GMT Monday) with a focus located off Wakayama prefecture, some 300 kilometres (185 miles) southwest of Tokyo.

There was no danger of tsunami tidal waves, the agency said.

Police in Wakayama and Shizuoka, prefectures most badly shaken by the quake, said they had no immediate reports of damage or injuries.

On Sunday two strong quakes measuring 6.9 and 7.4 on the Richter scale shook the same area within five hours of each other, setting off tidal waves. More than 40 people were injured but there was no major damage.

The government announced on Monday that Sunday's jolts were triggered on the same focus, but denied that they were a sign that a huge quake forecast by seismologists could strike the Tonankai region, the Pacific coastline of Wakayama.

In 1944 a massive earthquake measuring 8.0 on the Richter scale hit the area, killing at least 1,223 people. Seismologists forecast an equally powerful earthquake will jolt the same area in the first half of this century.

"Sunday's quakes are not regarded as a sign of an expected Tonankai earthquake," said an official at the government's earthquake research committee.

The committee on Wednesday will discuss whether the latest quake was a precursor to the next big one, he said.

The most frequently forecast scenario for another major earthquake in Japan is one that could devastate the Tokai region around Mount Fuji in central Japan.

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