Shares in German nuclear power plant operators RWE AG (RWE.XE) and E.ON AG (EOAN.XE)--the country's largest utilities--came under pressure Monday as explosions at Japanese reactors cast doubt over the controllability of atomic energy.

The accidents at Japanese nuclear reactors that followed a devastating earthquake and subsequent tsunami Friday re-ignited the nuclear debate in Germany--a country notoriously suspicious of nuclear energy.

Meanwhile, solar energy and wind power equipment makers gained sharply as investors anticipated the incidents in Japan could result in faster expansion of alternative and greener energy sources.

The nuclear disaster prompted German Chancellor Angela Merkel over the weekend to announce a thorough review of the safety standards of the country's reactors.

"On the question of safety, there can't and won't be any compromise," Merkel said, but added it is too early to tell whether the accident will have consequences for Germany's nuclear policy or the decision on the nuclear life-span extension.

German Environment Minister Norbert Roettgen also over the weekend said the accidents in Japan raise doubts about the use of nuclear energy.

"Nuclear energy is an obsolescent model," Roettgen said on ARD television. "Now the question is, whether the availability of alternative energies can be accelerated," Roettgen added.

Despite widespread rejection of nuclear power by the German population, the government last year decided to allow nuclear power stations to operate by on average 12 years longer than previously planned. The measure overturned a decision from a decade earlier to switch off Germany's last nuclear reactor in 2022.

The nuclear extension is part of a broader energy roadmap through 2050 which also includes targets for drawing more power from renewable energy, modernizing power grids, and improving efficiency.

Four decades from now, the government wants greenhouse gas emissions to be 80% lower and for some 60% of the country's power to come from renewable sources--up from about 16% today.

To make that goal more realistic, the lifespan of the country's 17 nuclear reactors will be extended, allowing them to serve as a "bridge technology," Chancellor Merkel's government has repeatedly said.

At 0929 GMT, RWE was down 3.5% at EUR46.25, while E.ON shares traded lower 3.1% at EUR22.37.

Shares in solar cell makers Q-Cells SE (QCE.XE) and SolarWorld AG (SWV.XE) as well as wind turbine maker Nordex SE (NDX1.XE) traded sharply higher, posting gains of 16.1%, 13.9% and 20.1% respectively.

-By Jan Hromadko, Dow Jones Newswires; +49 69 29 725 503; jan.hromadko@dowjones.com