BRUSSELS — Germany on Tuesday became the first European country to shut nuclear plants in the wake of the crisis in Japan as the European Union made plans to test all 143 nuclear power plants in its 27 countries.

Chancellor Angela Merkel of Germany said seven plants that went online before 1980 would be temporarily closed and the time would be used to study speedier adoption of renewable energy. All of the plants were built by German contractors.

While Mrs. Merkel asserted that safety was her main concern, opposition politicians accused her of pandering to fear about nuclear power ahead of a regional election this month. She has, in effect, suspended a decision last autumn to keep older plants operating beyond their previously designated life span.

The tests across the European Union are intended to ensure preparedness for emergencies like floods and tsunamis, as well as terrorist attacks, the European energy commissioner, Günther Oettinger, said after meeting with representatives of the nuclear industry, electricity companies and governments.

“This is a reassessment, if you like, of all potential risks in the wake of what has happened in Japan,” Mr. Oettinger said.

The Japanese disaster has led officials in Europe and the United States to think twice about nuclear expansion. But for now, developing countries, while acknowledging the need for safety, say their energy needs give them little choice but to continue investing in nuclear power.

A crucial element, Mr. Oettinger said, would be to determine whether the plants had enough backup power to cool the reactors if electricity was lost. The loss of backup power after the earthquake and tsunami in Japan led to overheating and explosions at the Fukushima plant.

Mr. Oettinger, who became energy commissioner with Mrs. Merkel’s support, appeared Tuesday to shift his attitude toward nuclear energy. “We must also raise the question if we in Europe, in the foreseeable future, can secure our energy needs without nuclear energy,” he told the German TV station ARD.

In his native state of Baden-Württemberg, where Mrs. Merkel’s party risks losing power in March 27 elections, Mr. Oettinger was known as a proponent of nuclear power. The state has two plants, one of which is among the seven to be shut down. On Saturday, about 50,000 protesters formed a human chain from the state capital, Stuttgart, to that reactor. On Monday, an estimated 110,000 people demonstrated in 450 towns across Germany against extending nuclear power.

Both Mrs. Merkel and Mr. Oettinger said President Nicolas Sarkozy of France would raise nuclear safety at the next Group of 20 nations summit meeting.

Mr. Oettinger said the tests should include as many plants in the European Union as possible. Nuclear power produces around a third of the electricity and 15 percent of the energy consumed in the European Union.

The chief executive of the German power giant E.On, Johannes Teyssen, said he would welcome more common standards for European nuclear safety. He declined, however, to rule out power cutoffs as a result of Mrs. Merkel’s decision, noting that “obviously depends on several factors of demand and supply, on availability of transmission grids, on a lot of issues.”

“With this new unbalance in the system, minor accidents can have major implications,” Mr. Teyssen said in Brussels. “We will try our best to live up to the situation, but the risk of the system has definitely increased.”

The industry made a similar threat almost a year ago when Mrs. Merkel agreed to extend the life of the power plants if the utilities paid a special tax. The utilities said the tax would hinder investment. Germany has 17 nuclear plants. They provide 26 percent of the country’s electricity; the seven older reactors produce about a third of that percentage.

European operators already face narrowing choices over where to locate reactors. In France, which relies on nuclear energy for more than 75 percent of its electricity, hot water discharged by power stations can combine with rising air temperatures to warm rivers enough in the summer to threaten fish and plant life. But building plants on seafronts, where cold water is abundant, may be less attractive because of storms and rising sea levels linked to climate change.

A total of 17 reactors in the European Union use technology similar to those affected in Japan, which are known as boiling water reactors, according to the European Commission. Of those 17, nine in Finland and Sweden are on coastlines, according to the Nuclear Energy Agency, part of the Organization for Economic Cooperation and Development.

About 40 percent of the reactors in the union’s member states are on coastlines, according to the commission.

The Continent has comparatively weak earthquakes. Even so, nature can pose a threat. During a storm in 1999, rising water levels in the Gironde River led to severe flooding at the French plant Blayais, shutting down some safety systems.

Since then, Électricité de France, which runs the plant, has improved protections at Blayais.

Stress tests would have common standards, Mr. Oettinger said, but “if you have a plant which is on the coast, well then obviously flooding and tsunamis will be tested for perhaps more thoroughly than plants situated at much greater altitude.”

 The nuclear crisis in Japan is also complicating the debate over whether to pursue nuclear energy in Chile, which only last year suffered an 8.8-magnitude earthquake that caused devastation, officials said this week.

 Next week, Chile and the United States are expected to sign a memorandum of understanding on nuclear cooperation when President Obama visits Santiago. But given the disaster in Japan, Chile’s energy and mining minister, Laurence Golborne, told reporters the government needed to study the situation.

“We may decide we don’t want this type of energy and we will have to analyze other sources,” he said. “The country needs energy, and to say no to something means saying yes to other things.”