Police believe the soldier, who was a part of a joint Indian-Australian defence force expedition rafting down the Franklin River and went missing in the state of Tasmamia's rugged south-west, has drowned. Eyewitness accounts have given police little hope of finding the man alive.

Attempts to retrieve the body of the soldier, who was not identified from the dangerous waters will have to wait until the river level drops.

"It is now reported to us that the Indian man was seen to fall whilst trying to get ashore at a portage around a rapid called the Cauldron," an Australian police officer was quoted as saying by the ABC News.

"The man was seen to enter the water but not resurface below the rapid. That leads us to the conclusion that potentially drowning is a real likelihood."

"The Cauldron, where this man's gone missing, is a jumble of large boulders - serious bus-sized boulders – just jumbling up the river," he said.

He says the surviving members of the rafting trip are believed to be holding up well. "I have spoken to the leader of the expedition. They're holding up reasonably well and the army are assisting police with the ongoing search," he said.