Kozloduy nuclear plant has now also cut output at reactor 6 because the Danube's water level is too low, the energy ministry and the plant say. Until now the cut only applied to reactor 5, while reactor 6 kept running as normal.

A working group in charge of the plant's safety when the river runs low made the call. The energy ministry and the electricity grid operator are coordinating the steps with the plant.

Between them, the two reactors are now producing 180 megawatts less, 90 each. Reactor 5's output was first cut on August 21, by about 120 megawatts. On August 31 it started to recover gradually, but on September 14 it was cut again, this time by about 60 megawatts.

The energy ministry says the August 21 cut was the first in the plant's 52-year history caused by drought and very low water in the Danube. It adds that forecasts point to the river level falling further, so more steps under the existing procedures cannot be ruled out.