The youngster was rushed to Yorkhill Hospital after the incident during the brilliant Bank holiday sunshine on Monday.

The boy's aunt, Anne Marie Young, witnessed the attack. She was in the village with her two sons and her nephew Aidan who is on holiday here from Australia.

The boys ran ahead as she walked along Stewart Street and Aidan went up to pat the Collie dog tied to a tree near the Cancer Research shop, when to her horror it turned on him and began biting his face.

The aunt explained: "It happened so quickly I could do nothing — I was distraught trying to comfort my nephew, wipe the blood which was pouring down his face and call an ambulance at the same time — it was a very frightening experience."

A police spokesman confirmed: "A report has been sent to the Procurator Fiscal under the Dangerous Dogs Act. The owner of a cross Collie dog had it tied to the tree while she went into the shops around 3.30pm on Monday.

"The owner, who returned to the dog while an ambulance attended and took the child to hospital, has since had the animal put down."

Anne Marie is urging parents to warn children about the dangers of approaching unattended dogs and added: "It can happen so easily. In this incident the dog did not bark or give any other indication it was unhappy.

"My boys are a bit more timid than Aidan who is more used to cuddling dogs. He was in no way antagonising the animal. I called for the boys to join me but he wanted to give it one last pat and as he did so, it turned on him with no warning.

"I want parents to impress on children how unpredictable an unattended dog can be."

A police spokesman also had a warning for dog owners who leave their animals tied up.

Milngavie community police officer Des Clark said: "Dog owners should not leave their animals unsupervised as their behaviour can often change very quickly — especially if the owner is not present

"If the owner had been in charge of the dog when the boy tried to pat it, there could have been a completely different outcome. Parents should urge children to admire animals from a safe distance."