Japan is evacuating tens of thousands of residents from around two nuclear power plants damaged in a massive earthquake, as the death toll from it and the tsunami it caused climbs.

Officials have warned of a possible radiation leak today as authorities battled to contain rising pressure at the plants 240km north of Tokyo.

Altogether, five nuclear reactor units which were shut down after the massive quake yesterday.

Officials say hundreds have been injured and hundreds more are missing after yesterday's magnitude 8.9 quake triggered a tsunami up to 10 metres high, devastating the country's northeastern coast.

It is feared more than a 1000 people are dead.

Underscoring grave concerns about the Fukushima plant, the US air force delivered coolant to avert a rise in the temperature of its nuclear rods but officials said a leak was still possible because pressure would have to be released.

Kyodo news agency reported that authorities had begun evacuating about 20,000 people from the vicinity of one of the plants.

The unfolding disaster prompted offers of search and rescue help from 45 countries.

Boats, cars and trucks were tossed around like toys in the water after a tsunami hit the town of Kamaichi in northern Japan.

Kyodo news agency reported that contact had been lost with four trains in the coastal area.

The extent of the destruction along a lengthy stretch of coastline suggested the death toll could rise significantly.

And as search and rescue teams are being mobilized, thousands are stranded on roof tops in buildings in the worst affected area in Sendai.

This report from the CNN.