The Krsko plant's alert was forwarded to all 27 European Union member states as part of the ECURIE early-warning system, which was established in 1987 after the nuclear meltdown in Chernobyl.

EU spokesman on energy issues Ferran Tarradellas said the system was used frequently, but warnings were seldom deemed serious enough to forward to all member countries.

Indeed, shortly after sounding the alarm -- which is reserved for emergency situations -- Slovenia played down the incident, saying that everything was under control and no damage had been caused to the environment.

"It was a mistake ... a genuine human error," Slovenia's Environment Minister Janez Podobnik told reporters via a translator outside the Luxembourg meeting of EU environment ministers on Thursday, June 5. "The nuclear safety agency has already apologised it used the wrong form," he added. "It used the form that had exercise (written) on it. There was no need for any protective measures for people and the environment. And only a very minor repair is needed."

The Austrian government however complained it had not been alerted properly.

"It must be immediately clarified and I will ask for that in the council," said Austrian Environment Minister Josef Proelle. "Why were the directly affected neighbours confronted with a test announcement? This should not happen."

Proelle added: "This places a serious question mark over our confidence in the Slovenian alarm system."

Germany's Environment Minister Sigmar Gabriel, on the other hand, said that the incident showed that the alarm system worked, even if it was unnecessary in this case.

No harm caused

The incident at the nuclear power plant in Krsko, Slovenia, was at the lowest level of emergency out of four levels as defined by the Slovenian Nuclear Safety Administration (SNSA), the International Atomic Energy Agency said on Wednesday, June 4.

"There is no danger for the people or the environment," said Maja Kocijancic, spokeswoman for the EU's Slovenian presidency. There was a leak of water, but not of radioactive material, she added.

According to SNSA, a loss of coolant was detected at 3:07 pm local time and the plant was shut down manually.

Plant director Stane Rozman said in an interview with Radio Slovenija that the shut-down was standard procedure and "nothing unusual." The problem would be located and resolved within a few days, he added.

Krsko in earthquake territory

The director of the Institute of Risk Research at the University of Vienna told ORF television on Wednesday that the Krsko reactor was a "good power plant" but was located in an earthquake-prone region.

The Krsko plant, in south-western Slovenia near the Croatian border, provides 20 percent of the country's energy needs and 15 percent of Croatia's. The power grid remained stable following the incident and the power deficit caused by the shutdown was compensated with imports from the Balkans and Germany, reported Radio Slovenija.

The 696-megawatt light-water reactor in Krsko was built by US firm Westinghouse and became operational in 1983. Jointly owned by Slovenia and Croatia, it is the only commercial nuclear plant in former Yugoslavia.

Although no damaged was caused, Wednesday's incident may reignite EU-wide discussions over the use of nuclear power. Several member states, including Germany and Italy, have already committed to phase out the use of nuclear power.

Environment group Greenpeace said the incident highlighted the danger of a nuclear resurgence within Europe to help reduce CO2 emissions.

"Those who are planning to build more nuclear reactors must head this warning and reject nuclear technology," said Greenpeace nuclear campaigner Jan Beranek.