Germany has announced the temporary shutdown of the oldest seven of its 17 nuclear reactors pending a safety review in light of Japan's atomic emergency.

Chancellor Angela Merkel has announced the launch of a safety review of all nuclear reactors in the country, with any reactors in operation since the end of 1980 set to be idle for the duration of the three-month moratorium.

This covers seven nuclear reactors in Germany, a country which decided a decade ago to be nuclear-free by 2020.

Last year, Ms Merkel's government postponed this target until the mid-2030s, despite strong public opposition.

Japan's government has said radiation levels near the Fukushima nuclear plant have reached levels harmful to humans, advising thousands of people to stay indoors after two explosions and a fire at the facility.

Four of the six reactors at the plant, 250km northeast of Tokyo, have now overheated and sparked explosions since Friday's massive earthquake and tsunami knocked out cooling systems.

'After this moratorium, which will run until June 15 ... we will know how to proceed,' Ms Merkel said following crisis talks in Berlin with premiers of German states where there are nuclear plants.

She said Germany would also use the period to discuss what to do with radioactive waste - no permanent storage site exists -boosting renewable energies, and international safety standards for nuclear power.

'Safety standards in Germany are one thing, they are important, but safety standards in Europe, being able to compare then, and international safety standards are also important,' Ms Merkel said.

Germany's older plants include one in Bavaria, two near Frankfurt and two in the southwestern state of Baden-Wuerttemberg, where a key state election takes place on 27 March, with nuclear power set to be a major issue.

A survey by public broadcaster ARD published today had 53% of respondents saying all reactors - which produce a quarter of Germany's power - should be taken out of service as soon as possible.

The poll of 909 voters showed that 70% thought that an accident similar to that in Japan could happen in Germany, while 80% want Ms Merkel to reverse the government's extension of operating times.

Germans have long been uneasy about the safety of nuclear power, with shipments of nuclear waste regularly attracting angry protests and Ms Merkel's decision sparking large-scale demonstrations last year.