An Austrian minister criticised Slovakia Thursday for concluding an environmental study on the expansion of a nuclear power plant without taking into account Vienna's concerns.

"It's an affront to Austria and I strongly condemn it," Environment Minister Nikolaus Berlakovich fumed after Bratislava gave the green light to the expansion of the Mochovce plant.

"This is not in line with our previous agreements," Berlakovich said in a statement, urging the government to lodge a formal protest.

Austria, which is strongly opposed to nuclear energy, has criticised Slovakia for not taking into account its concerns over safety systems at the plant, located 160 kilometers (100 miles) east of its capital Vienna.

The Mochovce plant has two Soviet-designed pressurised water reactors that were put into operation in the late 1990s after safety upgrades by Western companies.

Slovakia wants to complete another two reactors on which construction was halted in the 1990s due to a lack of finance, and has awarded contracts to the French group Areva, Germany's Siemens and Austrian building company Strabag.

The expansion, expected to cost 2.7 billion euros (2.9 billion dollars) should be completed in 2013 and cover 22 percent of the electricity consumption of Slovakia's population of 5.4 million.

The environmental group Greenpeace has filed a complaint with Slovakia's supreme court over the environmental impact study, claiming it was conducted by a company connected to one of the firms slated to build the new reactors.