A polar bear and a Canadian eskimo dog appear to have become unlikely friends, after a tour guide filmed the pair interacting happily.

David De Meulles told CBC News he took out two tourists who were hoping to see a polar bear close-up when they came across the strange sight in Churchill, Manitoba.

"I had no idea what was going to happen, and then sure enough he started petting that dog, acted like he was a friend," he said.

"I just so happened to catch the video of a lifetime."

He said it was a "beautiful sight to see".

"I've known the bears to have somewhat friendly behaviour with dogs, but for a bear to pet like a human would pet a dog is just mind-blowing," he said.

But University of Alberta adjunct professor Ian Stirling told CBC News the dogs should not be chained up outside in polar bear territory.

"The dog was chained up and they're totally vulnerable," he said.

"Inuit [hunters] over the years in the high Arctic have told me that if you want a dog to act as a guard dog, you have to leave it off a chain. Because if it's on a chain it knows it's vulnerable and it won't bark."

A polar bear's diet usually consists of seals, but they are also known to snack on land animals like reindeer, dogs and even other bears.