German police have launched a Europe-wide manhunt for a man suspected to be behind a series of acts of sabotage on electricity substations across Germany in recent days.

A 48-year-old man from Gevelsberg, near Dortmund, has claimed responsibility for the incidents in two letters seen by dpa on Friday. His motive is reportedly to draw attention to the production of electricity from fossil fuels, which he called a "crime."

"It first needs to be established whether he is actually a suspect or just a copycat," a police spokesman said. However, the letters reportedly included information about incidents that had not yet been publicized when they were sent.

Earlier on Friday, a suspicious device was found at an electricity substation in the western town of Dormagen, between Cologne and Dusseldorf.

Examinations of the object, which was discovered at the substation on Thursday evening, have not yet been completed.

According to German newspaper Bild, launching devices for homemade rockets were discovered. The report said timers and copper wires had been attached to the devices.

The letters also mentioned an upcoming attack on critical infrastructure at a power station near Aachen. Police then carried out a thorough search of the area around the Weisweiler power station.

A dpa reporter at the scene observed forensic officers wearing protective suits and breathing apparatus recovering numerous thin wires. Police are yet to confirm details about the operation.

The incidents came after others earlier this week in the western state of North Rhine-Westphalia and in Brandenburg, outside Berlin.

So far, no damage has been found apart from at a substation in Bergheim, west of Cologne, where unknown perpetrators placed cables across overhead power lines to cause a short circuit on Tuesday. Several launching devices were later discovered.

Police are searching for the 48-year-old and raided a property in his home town of Gevelsberg.

Herbert Reul, the interior minister of North Rhine-Westphalia, said: "There is considerable evidence to suggest that a person whose name we know is behind this."

"We took another look last night at the locations he mentioned," he added. "And indeed, it wasn't a hoax. At least the information is correct."

"At the moment, there is less to suggest a foreign power is involved. There is strong evidence to suggest it is a lone perpetrator. However, it could also be a group that is involved. And in that respect, we are waiting to see how things develop."

Police are on high alert across the country after the acts of sabotage.

In Ganderkesee, west of Bremen, a large operation was launched on the grounds of a substation early on Friday after a patrol observed an open electrical cabinet.

Officers searched the area but did not find any perpetrators or damage.