The attacks have led to power-generating units at some plants being temporarily taken off the grid.

A statement from the Cologne Public Prosecutor's Office and Cologne Police on Tuesday did not provide further details on the suspect, or on the number and whereabouts of incidents he has been linked to.

German media have previously reported receiving two letters from the suspect claiming responsibility for the attacks. The Frankfurter Allgemeine Zeitung said the handwritten letters contained information that had not yet been made public.

The letters were apparently signed with the first name Daniel, while his surname was kept anonymous, in line with German privacy rules. The letters also gave a residential address in the town of Gevelsberg.

Cologne Police had previously said it was searching for a 48-year-old suspect from the town in connection with the sabotage of electrical substations in three German states. Investigators had also said explosives were found during a search of the suspect's apartment.

In Saxony alone, police found 21 devices near high-voltage power lines last Friday and Saturday.

Interior Minister Armin Schuster has admitted it could have led to a regional blackout, but he has warned against jumping to conclusions.

"The way this deed was committed makes this case unusual, as well as the manner of the confession," he said.