Germany's electricity suppliers sought today to allay fears over the country's network after it emerged Europe's top economy imported power from neighbouring Austria last month to stabilise the system.

A spokesman for the federal agency in charge of the power network told AFP that "on December 8 and 9, reserve power stations in Austria were used."

Tennet, the firm that operates power lines across a large swathe of Germany, confirmed the emergency measures but stressed it was a "precautionary" step.

"There is no immediate danger for the security of supply," a spokeswoman told AFP, adding it was the "first and so far only time" this had happened.

The reserves were needed due to a series of exceptional circumstances, including the temporary shutdown of a nuclear plant in the south and problems transmitting power from wind farms in the north.

Several media reported the recourse to Austrian power, with the Berliner Morgenpost daily saying in a headline: "German power supply is no longer enough", describing the situation as "critical."

Papers also noted the unseasonally warm weather so far in the German winter had tempered the demand for power.

In the wake of the devastating earthquake and tsunami in Japan last March, which prompted radiation to leak at the Fukushima Daiichi nuclear plant, Germany decided to phase out nuclear power by 2022.

Eight of Germany's 17 reactors have already been switched off and the nine reactors currently on line are due to be turned off between 2015 and 2022.

Since August, officials have warned that an emergency system of reserves would need to be put in place, both in Austria and Germany, to cover resulting shortfalls and prevent blackouts.

Bottlenecks on the system would not be cleared until 2013 when new high-tension lines come on line.