Tsunami alert cancelled

A 7.1 magnitude aftershock has hit northern Japan, close to the epicentre of the 11 March magnitude 9 earthquake.

According to the US Geological Survey, the aftershock struck at 11.32 pm local time at a depth of 49 kilometres. A tsunami alert for two-metre-high waves was issued after the event but cancelled two hours later.

News reports, quoting statements from Tokyo Electric Power Company and Japan's Nuclear and Industrial Safety Agency, say there have been no unusual conditions reported at the stricken Fukushima Daiichi nuclear power plant. However, workers trying to cool the reactors damaged by the 11 March quake had to be evacuated.

More than 820 aftershocks have occured since the initial March 11 earthquake, according to a report issued earlier this week by reinsurance broker Aon Benfield. These aftershocks have caused damage to at least 203,000 homes, the broker said.