A German police officer shot and wounded a man who threatened another officer with a weapon in the car park of a Berlin hospital, but the incident did not appear related to terrorism, a police spokesman said.

"There are no signs whatsoever of terrorism, but rather of a mentally unstable person," the spokesman said.

German authorities have been on high security alert since December, when an Islamist militant drove a truck at high speed into a crowd at a Berlin Christmas market, killing 12.

The Berlin police spokesman said the motives of the man who menaced the police officer were not yet known and that he had said nothing while pointing his weapon.

He said the man was shot in the leg and underwent surgery at the hospital in the Kreuzberg district of Germany's capital.