‘‘We really need to have a better view of the operation in Europe,’’ Mr. Bailly said as energy ministers met. Nuclear safety will also be raised at the G-20 summit meeting, which will be held in France at the end of the month, Mrs. Merkel said, adding that she had already spoken with Nicolas Sarkozy, the French president.

Mrs. Merkel said the shutdowns in Germany were based on a government decree. Germany is one of the first European countries to halt operations at some reactors in response to the nuclear disaster in Japan. 

Mrs. Merkel made the announcement after holding emergency talks with the leaders of the 16 German states. The closure of the seven plants means that Germany will have to speed up the development of alternative energy sources, such as renewables, wind and solar power. 

It was not immediately clear if the seven plants would remain closed after the end of the three-month review period, said Environment Minister, Norbert Röttgen  who briefed reporters after the meeting.  On Monday, Switzerland joined Germany in saying that it would reassess the safety of nuclear reactors and possibly reduce reliance on them.

Doris Leuthard, the Swiss energy minister, said Switzerland would suspend plans to build and replace nuclear plants. She said no new ones would be permitted until experts had reviewed safety standards and reported back. Their conclusions will apply to existing plants as well as planned sites, she added. Swiss authorities recently approved three sites for new nuclear power stations.

Germany will suspend “the recently decided extension of the running times of German nuclear power plants,” Chancellor Angela Merkel told reporters in Berlin. “This is a moratorium and this moratorium will run for three months.” She said the suspension would allow for a thorough examination of the safety standards of the county’s 17 nuclear power plants.

“There will be no taboos,” Mrs. Merkel said.

Even when the three months is over, Mrs. Merkel warned, there would be no going back to the situation before the moratorium.

Across Europe, officials worried about the Continent’s use of nuclear power as cooling systems failed at a third nuclear reactor in Japan and officials in that country struggled to regain control.

The European Union called for a meeting on Tuesday of nuclear safety authorities and operators to assess Europe’s preparedness. Austria’s environment minister, Nikolaus Berlakovich, called for a European Union-wide stress test “to see if our nuclear power stations are earthquake-proof.”

In Germany, with Mrs. Merkel’s center-right coalition facing important regional elections this month, the move was apparently in part an effort to placate the influential antinuclear lobby and give her coalition some breathing space before making a final decision about nuclear energy.

The foreign minister, Guido Westerwelle, called for a new risk analysis of the country’s nuclear plants, particularly regarding their cooling systems. He is the leader of the pro-business Free Democratic Party, which strongly supports nuclear power.

A previous government, led by the Social Democrats and Greens, pushed through legislation in 2001 to close all of the country’s nuclear plants by 2021. But Mrs. Merkel’s center-right government reversed that decision last year and voted to extend the lives of the plants by an average of 12 years.

Nuclear energy provides about 11 percent of Germany’s energy supply but its contribution to electricity output is about 26 percent.

In Switzerland, the suspension of plans to build and replace plants will affect all “blanket authorization for nuclear replacement until safety standards have been carefully reviewed and if necessary adapted,” Ms. Leuthard, the energy minister, said in a statement.

Switzerland has five nuclear reactors, which produce about 40 percent of the country’s energy needs.

Ms. Leuthard said she had already asked the Federal Nuclear Safety Inspectorate to analyze the exact cause of the problems in Japan and draw up new or tougher safety standards “particularly in terms of seismic safety and cooling.”

In Russia, Prime Minister Vladimir V. Putin said his government would not revise its ambitious program of building nuclear reactors but would “draw conclusions from what’s going on in Japan,” Russian news agencies reported. Nuclear power currently accounts for 16 percent of Russia’s electricity generation.