A manhunt has been launched in Germany after a teenager boasted about stabbing his nine-year-old neighbour to death on a video uploaded to the dark web.

The footage came to light when another user of the dark web – a hidden part of the internet often used for criminal activity – alerted the local police force after the suspect sent him the video of him allegedly committing the crime and holding up his bloody hands.

The body of a boy with stab wounds was subsequently found in the basement of a house in the city of Herne in the western region of North Rhine-Westphalia, said Bochum Police spokesman Volker Schuette.

He said the victim and the suspect were neighbours.

Prime suspect, Marcel Hesse, may be armed and Bochum Police have warned the public not to approach him

The 19-year-old, who was not previously known to police, was as a loner with few friends and an expert in marital arts, according to German newspaper Der Spiegel.