Belgium has restarted an ageing nuclear reactor after a nearly two-year shutdown, angering neighbouring Germany which fears the danger of a Fukushima-style meltdown.

Power company Electrabel said it put the Tihange 2 reactor back online “in complete safety”. There had been opposition from officials in adjacent North Rhine-Westphalia, Germany’s most populous state.

Belgium has been hit by a series of nuclear mishaps in recent years, with three of the country’s seven reactors at one point closed, due in two of the cases to the discovery of tiny cracks in the reactor casings.

The Belgian nuclear authority in November gave the green light to restarting Tihange 2, as well as another reactor near Antwerp, in November, giving Electrabel permission to operate the plant until its legislated final closure date in 2023.

Garrelt Duin, North Rhine-Westphalia’s economy minister, had warned strongly against the relaunch of Tihange, calling it outright “irresponsible”.

Four of Germany’s 10 biggest cities – Cologne, Düsseldorf, Dortmund and Essen – are located within the state.

The city of Aachen, 40 miles (60km) from Tihange, said it had explored legal options to stop the reopening but without success.

Germany, unlike Belgium and France, decided to phase out what was a substantial nuclear energy programme after the 2011 disaster in Fukushima, Japan.

At the time Belgium also committed to a withdrawal from nuclear power but has backtracked due to a lack of reliable alternatives.