The official death toll has now risen to 8,450, with 12,931 people missing. But there was some good news after an 80-year-old woman and her grandson were found alive in the rubble of Ishinomaki city, Miyagi prefecture, nine days after the quake, said Japanese media and police.

.Attempts continue to stave off a meltdown at the Fukushima nuclear plant. Engineers are still working to restore power supplies to the plant's cooling systems, which were knocked out by the tsunami.

The new figure of a possible 15,000 dead comes from police in the worst-hit Miyagi prefecture, and does not include the thousands more dead and missing in areas to the north and south. It is looking increasingly clear that the death toll will top 20,000 people at least.

The authorities have begun building temporary homes for some of the hundreds of thousands of people - including an estimated 100,000 children - still sheltering at emergency evacuation centres.

Many survivors have been enduring freezing temperatures without water, electricity, fuel or enough food.

The destruction of the mobile phone network means people are queuing for hours to make their allocated phone call of one minute. And crippling fuel shortages mean long queues at some petrol stations.

Meanwhile, at the stricken Fukushima nuclear plant, firefighters have continued to spray water at the dangerously overheated reactors and fuel rods, in a desperate attempt to avert a meltdown. Engineers hope that restoring power will allow them to restart pumps to continue the cooling process, and have attached power lines to reactors 1 and 2, but it is unclear when they will attempt to turn the power back on.