Official toll is 1,000 – but true figure likely to be far higher

The estimated death toll from Japan's devastating earthquake and tsunami leapt tenfold yesterday as the world's third-largest economy struggled to deal with the crippling aftermath of what Prime Minister Naoto Kan has described as the worst crisis to face his country since the Second World War.

With the relief effort continuing for a third day amid plunging night-time temperatures, the scale of Friday's disaster was unfolding as official lists of those missing were being compiled.

The death toll reported by Japanese broadcast NHK last night stood at just under 1,600, but looked set to rise further. Police said that in Miyagi prefecture alone more than 10,000 people may have perished in the 7-metre tsunami waves that crashed in to Honshu Island's north-east coastline on Friday afternoon. Previous estimates over the weekend had hovered at around the 1,200 mark.

All across the quake-hit area reports came in of towns wiped off the map with thousands feared dead or missing.

There are concerns that as many as 9,500 people are missing in Minami Sanriku – roughly half the town's population. Further north, in the port town of Rikuzentakata, city officials confirmed yesterday that only 5,900 of the 23,000 inhabitants had made it to city shelters in the past three days. In Fukushima prefecture, officials said they were still unable to contact 1,167 residents, including 918 in the town of Namie alone.

In a sombre news conference, Mr Kan called on the people of Japan to unite in the face of its worst disaster in living memory. "The earthquake, tsunami and the nuclear incident have been the biggest crisis Japan has encountered in the 65 years since the end of the Second World War," he said. "We're under scrutiny on whether we, the Japanese people, can overcome this crisis. I am confident people can overcome these hardships if we stand united."

The scale of the rescue operation now needed for those affected by the earthquake is breathtaking, even for a country as wealthy and technologically advanced as Japan. New aerial footage has shown that hundreds of kilometres of coastline have been overwhelmed by tsunami waves caused by Japan's largest recorded earthquake.

More than 310,000 people across the region are being housed in evacuation centres. A further two million homes are without electricity and rescuers are struggling to reach some of the more remote areas.

Japanese television reported yesterday that up to 10,000 people are still cut off from emergency workers in the Miyagi, Iwate and Fukushima prefectures, the three states hit hardest by the earthquake. Many were reported to be holed up in schools, shopping malls and food factories that were either missed by the tsunami or were strong enough to withstand its force.

More than 100,000 troops – half of Japan's armed forces – have been called in to oversee the rescue operation and to carry out the task of searching for bodies in the wreckage of once-thriving coastal towns. The rescue effort has been hampered by more than 250 aftershocks, 30 of which have measured more than 6 on the Richter scale.

Friday's initial earthquake was so large that the US Geological Survey estimates that Honshu Island has moved 8ft to the west. Kenneth Hudnut, a USGS geophysicist, told CNN: "We know that one GPS station moved [eight feet], and we have seen a map from GSI [Geospatial Information Authority] in Japan showing the pattern of shift over a large area is consistent with about that much shift of the land mass." Japanese seismologists have upgraded the size of the quake to 9.

Last night, Japanese officials warned of a possible second explosion at the Fukushima Dai-ichi nuclear complex, following a blast on Saturday.