Tsunami warning issued after powerful quake strikes off coast of Japan

There were no immediate reports of injuries or damage, or any reports of abnormalities at the two nuclear power plants in the area

A powerful quake rattled northern Japan Sunday evening, followed by several more temblors, according to the Japan Meteorological Agency.

A tsunami advisory was issued. The earthquake, with a preliminary magnitude of 6.7, struck off the coast of Iwate prefecture at a depth of 10km (6.2 miles) below the sea surface, at about 5pm Japan time.

There were no immediate reports of injuries or damage, or any reports of abnormalities at the two nuclear power plants in the area. The agency issued an advisory for a tsunami of up to 1m (3ft) along the northern coastal region.

The advisory remained in place an hour after the initial quake. Public broadcaster NHK warned people to stay away from coastal areas because of the danger of tsunami, and warned more shaking could follow in the area. A tsunami of about 10cm (4in) was detected at Ofunato city in Iwate Prefecture, Ominato port, Miyako and Kamaishi, and subsequently as high as 20cm (8in) in the coastal area of Kuji, NHK said.

Tsunami waves that follow earthquakes can continue for a few hours afterward, hitting the coast repeatedly, and can possibly get bigger with time. More quakes, which could be aftershocks, were also continuing in Iwate Prefecture.

Bullet trains in the area were temporarily delayed, according to JR East railway operator. The quakes had caused power shortages, Kyodo News said. The US Geological Survey gave the preliminary magnitude for the initial quake at 6.8.Japan, which sits on the Pacific "ring of fire," is one of the world's most earthquake-prone countries. The area suffered a deadly earthquake and tsunami in March 2011.