He was responding to concerns expressed by Greenpeace Greece director Stelios Psomas who said in Athens on Wednesday that stray missiles hit Bulgaria dangerously close to its Kozloduy plant and oil spills in the Danube river could block the plant and cause a meltdown.

"Serious measures have been taken, which make it impossible for any slicks to float into the pumping station which delivers water for the cooling system," Kaschiev said.

He said the plant was supplied with special floating barriers to repell oil slicks, equipment to pump out oil and other installations.

Police, army, fire-fighters services and gendarmerie are monitoring land and river round the clock. Checkpoints have been installed on roads leading to the plant.

"Even if water supply (from the river) is cut, the reactors will switch off and will be cooled with water from alternative water suppliers we have at place including reservoirs," Kaschiev said.

The Kozloduy plant is situated on the banks of the Danube river, some 100 km (62 miles) from the border with Yugoslavia.

Five stray NATO air-to-ground HARM missiles and another Russian-made missile have hit Bulgarian territory near the western border with Yugoslavia, between 10 km and 40 km (22 miles) inland. One of the HARM wrecked a house in suburban Sofia.

"It is important to comply with the no-fly zone around the Kozloduy plant," Kaschiev said, adding that air defence missile systems had been installed near the plant.