Onlookers apparently shouted "Jump!" before a teenage migrant leapt from an apartment block in an eastern German town, suffering fatal injuries, the mayor said on Saturday.

Officers were called to the building in Schmoelln on Friday afternoon by the caregiver for a group of young migrants, who reported that a 17-year-old Somali boy was acting violently, police said. When they arrived, he was sitting on a fifth-floor window ledge.

Police and fire officers tried to persuade the teenager not to jump, but he leapt and died shortly afterward of his injuries.

"There is information that some ... onlookers spent a long time watching this incident and there were apparently shouts like 'go on, jump!'" Mayor Sven Schrade said.

"One can only condemn something like this," he added. "If someone takes it as an experience like a movie and then thinks they have to shout encouragement too, that's an unbelievable act."

A county official, Matthias Bergmann, said some people apparently took photos from nearby balconies during the incident, local broadcaster MDR reported.

A police report issued shortly before Schrade spoke to reporters did not mention either the alleged goading or the photos.

MDR said that the boy had been living in the area since April and had returned earlier Friday to the apartment in Schmoelln, shared with other young migrants, from a week at a psychiatric clinic. It said he had been suffering from depression.

Germany saw some 890,000 migrants arrive last year, and anti-migrant sentiment grew amid the influx.