Tokyo (AFP) - A strong earthquake struck off the coast of northern Japan for a third consecutive day early Sunday though there were no immediate reports of people injured or damage.

The shallow 6.0 magnitude quake hit at 00:58 am (1558 GMT Saturday) 170 kilometres (105 miles) east-northeast of Miyako city, the US Geological Survey said. It was followed by a 5.3 aftershock.

There was no threat of a tsunami following the quake, said the Japan Meteorological Agency, which measured it at a slightly lower 5.9 magnitude.

The tremors came seven hours after another 6.0 magnitude quake struck the same area on Saturday and also followed a 5.3 magnitude jolt which hit due east of Miyako on Friday.

Japan sits at the junction of four tectonic plates and experiences a number of relatively violent quakes every year, but rigid building codes and their strict enforcement mean even strong tremors often do little damage.

A massive undersea quake however that hit in March 2011 sent a tsunami barrelling into Japan's northeast coast, leaving more than 18,000 people dead or missing, and sending three reactors into meltdown at the Fukushima nuclear plant.

In April, two strong earthquakes hit southern Japan's Kumamoto prefecture followed by more than 1,700 aftershocks, and left 49 dead and caused widespread damage.