The epicentre of the quake was Rudraprayag district in Uttarakhand, said J L Gautam, Operations head at the National Seismological Bureau, a unit of Ministry of Earth Sciences.
A strong earthquake struck northeast of Tokyo today but there was no fear of a tsunami, Japan's meteorological agency said.
"Eighteen have died so far, based on data from the hospital. Some of the fatalities are children," Said Mulyadi, deputy district chief of Pidie Jaya, the region hit hardest by the quake, told AFP.
There were no risks of seismic waves or immediate reports of damage from Thursday's quake, which struck at 6:23 am (local time) off Fukushima prefecture some 210 kilometres northeast of Tokyo, Japanese authorities said.
A some three metre tsunami could hit the northeastern coast, the agency said, including Fukushima -- home to the Fukushima Daiichi nuclear power plant, site of one of the world's worst nuclear disasters.
The tsunami struck at 6:38 am (local time), a TEPCO official told a televised news conference after a magnitude 6.9 earthquake hit the region earlier.
The Japan Meteorological Agency said no tsunami warning had been posted. The Pacific Tsunami Warning Center said "a destructive pacific-wide tsunami is not expected."
The quake, at a relatively shallow depth of 10 kilometres, struck shortly after 2:00 pm (0500 GMT) in Tottori prefecture.
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An initial "potential" warning was upgraded to a tsunami after a wave measuring 30 centimetres was generated near the sparsely populated East Cape about 90 minutes after the earthquake struck.
The quake struck at a depth of 212 kilometre at 7:18 am (local time) some 31 kilometre southwest of the island of Agrihan, according to the US Geological Survey.
The quake, which occurred at a depth of 10 kilometres (six miles) was originally measured at 7.3-magnitude by the National Tsunami Warning Center (NTWC).
The epicenter of the quake, which struck at 8:33 GMT at a depth of 15.7 kilometers (9.8 miles), was located 25 kilometers west of Muisne and 73 kilometers west-southwest of Propicia, the US Geological Survey said.
There were no immediate reports of damage, but the shallower a quake, the more dangerous it is. The US Geological Survey originally put the magnitude at 8.2, and then 8.1, before lowering it to 7.9
No tsunami warning was issued and NHK national television said that while there might be some changes in sea level, no tsunami damage was expected.
The quake, which struck 150 km (90 miles) southwest of the town of Arawa, was relatively shallow, at 10 km (six miles). There were no immediate reports of damage or casualties.
A major earthquake with a magnitude 7.7 struck off Papua New Guinea on Monday, official monitors said, and a tsunami warning was issued soon after.
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An earthquake with a preliminary magnitude of 7.0 struck islands off northern Japan on Friday but no tsunami warning was issued, the Japan Meteorological Agency said.
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An earthquake with a preliminary magnitude of 6.2 jolted eastern Japan on Monday, public broadcaster NHK said, adding that no tsunami warning had been issued.
A powerful 8.0 magnitude earthquake set off a tsunami that killed at least five people in a remote part of the Solomon Islands on Wednesday and triggered evacuations across the South Pacific as island nations issued tsunami alerts.
Japan's Meteorological Agency said on Wednesday it expects a 20 cm (8 inch) tsunami to reach the country at around 4:30 p.m. (0730 GMT) after a strong earthquake struck near the Solomon Islands earlier in the day.
A powerful magnitude 6.7 quake struck central Chile on Wednesday, the US Geological Survey said.