Berlin - Chancellor Angela Merkel vowed Thursday that Germany would speed up the transition to renewable energy as Europe's top economy mulled a "measured exit" from nuclear power after the events in Japan.

"We want to reach the age of renewable energy as soon as possible. That is our goal," the chancellor told parliament during a fiery speech that drew frequent opposition jeers, indicating the depth of passion over the issue.

Merkel, a former environment minister, called for a "measured exit" from nuclear power and said "everything would be put under the microscope" during a three-month study to consider the future of energy policy in Germany.

On Monday, she announced a three-month moratorium on plans approved last year to postpone by more than a decade, until the mid-2030s, when the last of Germany's 17 nuclear reactors are turned off.

"We cannot and should not just go back to business as usual," Merkel told parliament.

On Tuesday, she ordered the temporary shutdown of Germany's seven oldest nuclear reactors while authorities conduct safety probes. At least one was mothballed for good.

"When the apparently impossible happens in such a highly developed country as Japan ... then the whole situation changes," she said.

In a desperate bid to cool fuel roads and prevent a catastrophic radiation release, Japanese military helicopters were on Thursday blasting the Fukushima nuclear power plant northeast of Tokyo with water.

Fears of a nuclear meltdown in Japan have grown since Friday's deadly earthquake and resulting tsunami.

Merkel added that switching to renewable energy would require a "broad consensus" in society and in parliament.

The Social Democrats (SPD) and ecologist Greens vociferously shouted their opposition in parliament, concerned that the moratorium will be no more than a brief delay in the country's nuclear progress.

"We want to go back to a nuclear exit in 2020," said SPD leader Sigmar Gabriel.

Merkel said she was confident that the economic impact of the disaster on the tottering global recovery would be relatively contained.

Although the economic fallout is "incalculable", she said: "I do not fear significant damage for the world economy."

"However, and I want to emphasise this, we will be working with our international partners to see how we can best minimise the impact," she added.

But if the economic consequences are difficult to foresee, the political fallout for Merkel of the heated nuclear debate could well be highly damaging.

Polls consistently show that nuclear power is unpopular in the country and protests against it regularly attract large crowds.

More than 100,000 people turned out on Monday to call for the closure of the country's nuclear facilities across more than 450 towns and cities, according to anti-nuclear campaigners.

In a separate protest on Saturday, tens of thousands formed a 45-kilometre (28-mile) human chain between a nuclear plant and Stuttgart. The demo was planned beforehand, but events in Japan swelled numbers.

It took place in the southwestern state of Baden-Wuerttemberg, where on March 27, Merkel's centre-right Christian Democrats (CDU) face losing power after 58 years in charge in a vital state election.

The SPD in Baden-Wuerttemberg have vowed to switch off the state's two oldest nuclear power stations by 2020 if they win the election. Polls suggest a tight race.

Gabriel accused Merkel of "electioneering" ahead of the vote.

Source: Agence France-Presse