Two western German states said Tuesday they planned to file a complaint at the EU and UN against Belgium over its ageing nuclear reactors which had their lifespan recently extended to 2025.

The Doel 1, 2 and Tihange 1 power stations have been in service since 1974-1975, and were scheduled to be shut down in 2015.

But the Belgian government in December decided to extend the lives of the 40-year-old reactors to 2025, under a deal to preserve jobs and invest in the transition to cleaner energy.

The states of North Rhine-Westphalia and Rhineland-Palatinate claimed however that before such a decision could be made, an environmental impact assessment had to be carried out, under a little known international convention called Espoo.

"The impact of an accident in Tihange and Doel would not be stop at the border of Rhineland-Palatinate," said the state's energy minister Eveline Lemke, stressing that decisions to extend nuclear plants' lifetime could not be imposed without consultations with neighbouring countries.

The reactor at Tihange is located just 60 kilometres (37 miles) from the German border while Doel is about 130 kilometres away.

Belgium's creaking nuclear plants have been causing safety concerns with its neighbours for some time now after a series of problems ranging from leaks to cracks and an unsolved sabotage incident.

Doel 1, the country's oldest reactor, was originally shuttered in February 2015 under a law calling for the country's gradual phaseout of nuclear power, but the government then restarted it under the extension deal.

But the plant, about 15 kilometres as the crow flies from the major port city of Antwerp, had to be closed three days later due to a generator problem. It has now restarted a second time.

Meanwhile Belgian operator Electrabel said in December it had restarted a reactor at its Tihange plant, just days after being forced to shut it down following a fire in the electricity supply system.