Tens of thousands of demonstrators on Sunday formed a human chain stretching from Germany, through the Netherlands and into Belgium, to highlight safety concerns over two nuclear reactors in Belgium.

Calling for the immediate closure of Belgium's Tihange 2 and Doel 3 nuclear power plants, about 50,000 protesters formed a tri-national, 90-km long human chain that stretched from Aachen, Germany, to Liege, Belgium, and Maastricht, the Netherlands.

"These nuclear plants were built in the 70s," one of the protesters told Ruptly TV. "They were not made to last so long, and we've been prolonging their lifetime, and this is extremely unusual."

Tihange, located some 20 kilometers (12.4 miles) southwest of Liege, and Doel, not far from the Belgium's port city of Antwerp, have both been subject to controversy over a number of safety incidents. Both 33-year-old reactors were closed in 2012 and again in 2014, after inspections found small cracks in their structures, but in 2015 the Belgian nuclear regulator authorized the plants' restart.

The regulator also dismissed last year's request by German Environment Minister Barbara Hendricks to shut down the reactors until unresolved safety questions are cleared up.

Thousands form human chain to protest against Belgium's nuclear reactors https://t.co/vmxGSvDlRs pic.twitter.com/kRf2IQ7npE — Luca de Ioanna (@io_luca) 25 июня 2017 г.

​The city of Aachen and some 100 communities in the border region filed a lawsuit against the operators of Tihange 2.

The administrative head of the Aachen city region, Helmut Etschenberg, described the demonstration, organized by a number of environmental organizations in all three countries, as "the strongest message the region could send," Deutsche Welle reported.