An observant webcam watcher has saved the life of a 72-year-old man floating in the Elbe River in the busy northern German port city of Hamburg.

Hamburg water police received a call from an internet user early Thursday morning saying he had seen the man drifting in the river on a webcam attached to a ferry pier, the Hamburg fire brigade said.

Several small boats and police divers were sent to rescue the man who was too weak to grasp the lifebelt they threw him.

When emergency workers pulled him on board lifeboats the man appeared to be suffering severe hypothermia.

It is still unclear exactly how the man ended up drifting in the river although local media reported he had fallen in near a path next to the water.