A German man who had been drinking heavily at Munich's Oktoberfest beer festival got stuck in a chimney for 12 hours while trying to climb into a friend's apartment, police say.

After finding his friend was not at home, the 27-year-old climbed on to the roof of a neighbouring building at about 2:00am and headed for what he thought was a gap in the wall between the two houses.

He found himself sliding almost 30 metres head first into a chimney, a spokesman for Munich police said.

An 82-year-old janitor from the hotel next door eventually heard the man's calls for help and he was rescued at around 2:00pm by fire brigade officers who knocked a hole into the side of the chimney to liberate him, the spokesman says.

He had managed to turn around and had removed his clothes to try to help him squeeze back up.

"Miraculously, he was only slightly injured in the fall, sustaining just grazes and bruising," police said.

The man was taken by helicopter to the hospital, where he is being treated for hypothermia, they added.

- Reuters