Japan awoke to another large aftershock this morning, while a fresh fire broke out at the stricken Fukushima nuclear power plant.

The magnitude-6.3 earthquake struck off the coast of Chiba prefecture, east of Tokyo, and was felt across the capital.

The tremor brought trains in Tokyo to a standstill but there was no threat of a tsunami along the east coast.

Soon after the earthquake hit, media reports emerged of a new fire in reactor No. 4 at the Fukushima nuclear plant.

Crews soon extinguished the fire and it was not clear how serious the situation had been.

The fire and the earthquake did not appear to be connected.

Japan has been rocked by aftershocks since a giant earthquake and tsunami killed thousands of people a month ago.

Last night a powerful 7.1-magnitude aftershock killed four people, including a 16-year-old girl who was caught in a mudslide.