The machine gun emplacement, built during World War 2, but now under attack from a mystery dog walker or walkers, lobbing their poop bags through the gun slit.

The guns have gone silent, the soldiers returned home - but now, someone has let slip the dogs of walkies on a piece of New Zealand military history.

A World War II machine gun emplacement on the beach at Plimmerton, Porirua, has come under attack from "disrespectful" dog walkers and their plastic poop bags.

Built in 1942, the concrete bunker housed a machine gun, pointed towards the harbour through a slit in its front. In the past its key vulnerability might have been to hand grenades, tossed through the openings.

Joel Maxwell The pile of dog poop bags scattered across the floor of the historic gun emplacement.

Now a shocked visitor to the site has posted photographs to Facebook of the emplacement interior piled with plastic bags of dog poop lobbed inside through its gun slits.

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Speaking to Stuff the man, who did not wish to be named, said he found the poop on Wellington Anniversary Day while out walking.

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A visit to the site on Wednesday by Stuff found the floor still covered with dozens of the dog poop bags, a jandal, and a partially eaten meal of fish and chips.

The man suggested the slits in the structure should be sealed with something like plexiglass - allowing people to see in, but not able to enter or throw things inside it. The dog walkers were "disrespecting" our history, the man said.

In a written response to queries, Porirua City Council said it was "obviously disappointing to see the machine gun emplacement, which is part of the Taupō Plimmerton Heritage Trail, being treated by some dog owners as a dog poo receptacle".

Joel Maxwell The side view of the machine gun emplacement that has no last line of defence against a dog on a leash.

"We'll arrange for a streetworks team to go and do the unpleasant job of cleaning it out, but this is a good time to remind all dog owners to pick up after their pooches. This means bagging and disposing of dog poo in an appropriate way – in a public litter bin, or at home."

The council had contacted the local residents association "so the community can help keep an eye out for this kind of behaviour".

Army and Home Guard members kept watch from the emplacement and other nearby bunkers for enemy forces arriving at Porirua Harbour.

Joel Maxwell History has come under attack in Plimmerton, Porirua, with dog poop repeatedly dumped inside this machine gun emplacement.

It was built between 1942 and 1943, during WWII as part of New Zealand's coastal defences.

The only access in or out of the bunker now appears to be through the gun slits.