Residents on a remote island in the Northern Territory were shocked to see what looked like a Viking ship sail past yesterday.

Police say they received a report of residents seeing the unusual boat off the coast of Elcho Island in Arnhem Land.

Northern Watch Commander Gary Smith says the 15-metre boat was a replica Viking vessel on the home stretch of a world tour.

"Police and local rangers patrolled the area and came across the vessel with swords drawn," Watch Commander Gary Smith said.

"It was established that the Viking vessel was a replica, it was crewed by six Russians who had sailed from Europe, down through Africa, Thailand, Indonesia and on to Darwin, where it was making its way to Sydney where the vessel is to be placed in a museum."