Police are hunting a hitchhiker who robbed American twin brothers of their car and all their possessions after befriending them.

Adam and Alex Rahmlow, 21, were left with only $20 and a tent after the man, they knew as "Rusty", disappeared with their car in Christchurch on Friday morning.

Rusty had stayed with the tourists at their campsite on the Ashley River for three days sharing their food with him after he told them a sob story of having his money accidentally direct-credited out of his bank account, The Press reported.

The Rahmlows said they had contacted their parents in Milwaukee who had cancelled their credit cards and made sure they were alright.

What frustrated them was the loss of their possessions and the contact details they had gathered over their six-month trip through Asia and especially Vanuatu, where they had worked for a few months for the United States Peace Corps programme.

The twins said Rusty claimed to have a house and job in Auckland and said he had been in the South Island on holiday.

Their car, a 1994 Mitsubishi Lancer, was worth only about $1500 and was not important to them, they said.

While they were not in a position to give a reward, "if we get most of our possessions back we'll give them the car," Adam said.

The theft had been reported to the New Brighton police.