German police said Thursday that they had arrested a 35-year-old man suspected of using package bombs to blackmail DHL, the parcels and express delivery service of Deutsche Post.

The suspected blackmailer, who turned himself into the police on Wednesday, is believed by investigators to be the culprit behind a series of extortion attempts which shocked Germany three years ago.

Investigators said the man had sent numerous explosive packages to addresses in Berlin and Brandenburg, the state which surrounds the capital, between November 2017 and 2018, without however causing injuries.

They included a DHL parcel containing nails, screws and explosive powder from Polish fireworks, which was received by a pharmacy in the city of Potsdam.

That package failed to detonate upon opening, but police nevertheless cleared the nearby Christmas market as a precaution.

The evacuation revived fears of the jihadist attack on a Berlin Christmas market attack a year earlier, which killed 12 people.

Police later discovered a message inside the package threatening further parcel bombs unless DHL made a 10-million-euro ($12-million), untraceable payment in the virtual currency bitcoin.

Though the man was arrested and charged on 10 counts of attempted extortion, a judge allowed him to remain free for now, pointing to the fact that he had turned himself in.