The leak on Sunday came from the main circuit pipe in the second block of the plant, located in the south of the country, 60 kilometers (35 miles) from the Austrian border.

"This is nothing serious," the spokesman said, adding that the water was contained in the area.

The block is currently closed to allow a faulty transformer to be replaced.

"The nuclear reaction has been stopped for a few days and we expect its relaunch in mid-June," Nebesar added.

Attributed to "a fault in the airtightedness", the incident happened inside a zone with a special floor fitted for such a type of leak, Zdenek Prouza, spokesman for the Czech Office of Nuclear Safety, told AFP.

The incident was first revealed by the Upper Austrian regional government on Monday, as the information was reported under a bilateral agreement between the two countries.

The plant, which was begun in the mid-1980s under the communist regime, has fuelled controversy since its launch in 2000 with nuclear-free Austria campaigning for its closure ever since.

Austria's environment minister Josef Proell called on the Czech Republic to mount a thorough investigation into the leak and demanded "improvements to security at the Temelin plant".

WAR.WIRE