• Johann Westhauser, 52, was injured when hit by rocks on Sunday morning
• He is thought to be 3,280 ft underground in Reinsending cave system
• Two doctors could be with the man within hours, rescuers said today
  
• Will then decide how to get explorer out - a mission which may take days

Germany's mountain rescuers says doctors are close to reaching an injured cave explorer - who has been stuck deep inside an Alpine cave on the Austrian border since Sunday.

Researcher Johann Westhauser, 52, was injured in a rock fall 3,280 feet underground inside the Riesending cave system near Berchtesgaden.

Rescue official Robert Nagel today said two doctors are on their way to the site of the accident - some 6,000 meters from the entrance.

He says they could reach Westhauser within hours and will then assess how the German can be brought to the surface.

Nagel says the tricky terrain within its vertical shafts and narrow passages means it will take about six days to bring Westhauser out.

Since the accident, more than 80 mountain rescuers - who reached the explorer on Monday - have been working to free him.

When rescuers reached Mr Westhauser, they found he had suffered head and upper body injuries a day earlier in a rockfall deep inside the caves.

The accident happened more than three miles from the cave entrance, and access to the site requires covering tricky terrain such as vertical shafts and bottlenecks.

Mountain rescue official Klemans Reindl said his colleagues were at work 'in one of the most difficult caves in Europe', access to which is complicated by water and tight spots.

'We have shafts that go straight down 350 metres (1,150 feet), where you have to rappel down and climb back up on a rope,' he told Germany's n-tv television.

The rescue service has set up a radio communication system that allows rescuers to send text messages to the surface.

On the day of the accident, one of the explorer's companions made a 12-hour solo climb back to the cave entrance to call for help, while the other stayed with him.

Mr Reindl said the cave system has tight spots where only a slim person can squeeze through, and explorers also have to contend with water.

Another mountain rescue official, Stefan Schneider, told a televised news conference: 'It's going round the clock, and it's going to last a few more days.

Rescuers working in several small teams of up to four people each have laid a telephone line several hundred metres along the route to help with their efforts.

Others have set up camps inside the cave system, which lies on the border with Austria.

Fifty-two cave rescue specialists from Bavaria, 28 from Austria and some from Switzerland were at the scene.