A strong earthquake with a magnitude of 7.1 hit Japan's north-eastern coast today, triggering a tsunami warning for the area still recovering from the devastating quake and killer wave four months ago.

Residents in coastal areas were warned to evacuate, but there were no immediate reports of damage.

The quake hit at 9.57am local time (1.57am BST), and a warning of a possible tsunami was issued for most of the north-eastern coastline.

The epicentre of the quake was in the Pacific Ocean off the coast of Japan's main island Honshu, at a depth of about six miles.

Officials said they expected tsunami of less than one metre in some areas.

Japan's north-eastern coastline was devastated by an earthquake and tsunami on March 11 that left nearly 23,000 dead or missing and sparked a nuclear crisis at a badly damaged facility in Fukushima.

Officials said there were no reports of abnormalities at the Fukushima plant caused by today's quake. Airports in the area were also functioning normally.

Japan is one of the world's most earthquake-prone countries. Dozens of strong aftershocks have been felt since the March 11 disaster, which measured a 9.0 magnitude and was the strongest in Japanese history.

Today's quake registered four on the Japanese scale of seven, meaning it was felt as moderately strong. Because of the damage from the March quake and tsunami, however, many buildings in the area are structurally weak and sea walls have been destroyed, making the region more vulnerable to relatively weaker quakes.