A trainee sniffer dog was shot dead after it escaped its handler and grounded flights at an airport in New Zealand, sparking fury from animal rights groups and members of the public.

The 10-month-old puppy called Grizz could not be captured after it ran off and shooting the animal was a last resort, an official at Auckland Airport said.

The incident grounded 16 flights and caused several hours of delays, they added.

Grizz was being trained by the government Aviation Security Service (Avsec) to detect explosives.

Avsec spokesman Mike Richards said it was getting into a dog unit wagon parked in the airport's public landside area, when “something” caused it to escape.

The animal then managed to run through an open gate onto the tarmac.

Mr Richards said a “massive effort” was launched immediately to locate the dog in pitch black conditions, but for the first two hours Grizz could not be found despite all of the service's off-duty dog handlers being called in to help.

When Grizz was located the dog would not let anyone near it and kept sprinting across the runways to escape.

“We tried everything, food, toys, other dogs, but nothing would work," Mr Richards said. "The area is too vast and too open to try and use mobile fencing.”

He added Grizz was on an "initial airport environment socialisation programme as part of his training before undertaking block courses and assessments including the critical task of identifying explosives.

"He did not have a permanent handler so was less responsive than a dog with a permanent handler."

Eventually a decision was taken to shoot the creature, which he said had left staff "naturally quite shaken", although he said they understood "the reasons for the decision".

However, New Zealand animal rights organisation Safe said it was “appalled about the needless killing of this dog”.

“A tranquilliser gun should have been used after efforts to catch the dog failed. If such a gun was not available - which it should - then they could have borrowed one from Auckland Zoo or elsewhere,” a spokesman told the New Zealand Herald.

Members of the public asked similar questions in slew of angry comments on the airport's Facebook page.

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Asked by the BBC why the dog could not be tranquilised, an airport spokeswoman said: ”I do not have the answer to that. But there were no tranquiliser guns at the airport, and the police do not have them either.“

She said tranquilisation would be part of an incident review undertaken by Avsec.

Callum Irvine, head of vet services at the New Zealand Veterinary Association added that tranquilising an animal was complex.

“There just isn't ready access to tranquiliser guns and darts in New Zealand, and even if authorities did manage to get their hands on one in time, there are so many other factors to take into consideration, like how close the animal is, the animal's weight, age and how much adrenaline was also running through the body,” he told the Stuff website.