(LUXEMBOURG) - Slovenia apologised Thursday to its European neighbours after wrongly informing them that an incident at a nuclear power plant was an excercise.

Slovenian Environment Minister Janez Podobnik told other EU environment ministers he was sorry for the mistaken alert, triggered after a leak in a primary cooling system at the country's only nuclear reactor. Neighbouring Austria reacted angrily.

"The Slovenian minister offered us his apology. For us, the incident is closed," Italian Environment Minister Stefania Prestigiacomo told reporters. A Slovenian official said that Austria "had been reassured".

Slovenia is current president of the EU and speaking as he arrived for the meeting, which he chaired, Podobnik said Slovenia's nuclear agency had "used the wrong form. It used a form that had 'exercise' on it. It was a mistake that was a genuine human error."

He said the error following the coolant leak Wednesday at the Krsko nuclear plant, which has been shut down, was spotted "in a few minutes" and corrected.

Austrian Environment Minister Josef Proell, whose country is deeply opposed to nuclear power, was furious about the mix-up.

"It's not okay to set off an alarm in Europe and inform Austria, Italy and Hungary that it's only an exercise," he said.

"The Austrian authorities have conducted tests at the border but they have not detected any increased radioactivity," he added, insisting: "There is no absolute security when it comes to nuclear power."

The correct procedure was used to notify the European Commission, which then issued an EU-wide alert.

An EU official said Slovenia was not obliged to warn at all about the leak -- spotted in the primary cooling system and causing staff to shut down the plant -- unless the government had to "take action of a widespread nature".

However the mix-up raised questions about procedure in such incidents.

"We will certainly have to ask: 'Why did you do it?'," said German Environment Minister Sigmar Gabriel, even though he conceded: "I prefer to have an unnecessary alert, than to have too few alerts."

The Slovenian official said an investigation would be launched.

Slovenian ministers said, the leak posed no threat and was expected to be repaired in a few days.

"The information I have this morning is that nothing problematic happened," said Interior Minister Dragutin Mate, as he arrived for a meeting of EU interior ministers.

"The environment is not polluted, everything is OK. It's a stable situation," assured Mate.

The EU's executive arm activated its European Community Urgent Radiological Information Exchange (ECURIE) system late Wednesday, immediately transmitting the information to all 27 member nations.

The system was introduced in 1987 after the Chernobyl disaster to provide early notification "in the event of a radiological or nuclear emergency".

EU energy spokesman Ferran Tarradellas Espuny rejected accusations that the commission had sown panic by using it.

"We've been asked on a number of occasions to be transparent and to deal with nuclear power in the same way as any other activity. We weren't sowing the seeds of panic," he said.

The Krsko nuclear plant, co-owned by Slovenia and neighbouring Croatia and located some 100 kilometres (60 miles) east of the capital Ljubljana, was built in the late 1980s and has a net electrical output of 696 MW.

It produces 20 percent of all electricity used in Slovenia and satisfies 15 percent of Croatia's power needs.

Text and Picture Copyright 2008 AFP. All other Copyright 2008 EUbusiness Ltd. All rights reserved. This material is intended solely for personal use. Any other reproduction, publication or redistribution of this material without the written agreement of the copyright owner is strictly forbidden and any breach of copyright will be considered actionable.