A strong 7.3 magnitude earthquake hit northeastern Japan early Tuesday, with the country's meteorological agency issuing a tsunami warning for the region's coast, including Fukushima prefecture, public broadcaster NHK said.

A some three metre (9.9 feet) 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.