Armed officers were deployed after an eight-year-old boy discovered a loaded shotgun.
A search of the area in Knotty Ash, Merseyside, was conducted on Sunday after police were called at about 2.20pm following the weapon being found by the youngster in a fenced-off area outside an electrical generator along Kingsheath Avenue.
Chief Inspector Peter Clark, of Merseyside Police, said: "On this occasion the young boy has been extremely lucky that he hasn't come to any harm after finding this gun.
"He managed to take the weapon to his grandma who rightly called the police straightaway – but it sends shivers down my spine to think what could have happened. It is hugely worrying that whilst children are out playing that they can find such a dangerous weapon like this.
"I would urge anyone that has seen someone acting suspiciously to get in touch with us.
"It is not safe at all to handle guns, store, use or hide guns. If you know who this might belong to, get in touch quoting crime ref: 20000361262 and if you know anyone involved in criminal activity, let us know."
It is not the first time guns have been discovered close to areas where children may play.
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In February, police in Kirkby found a shotgun dumped near a school and hidden in a rucksack.
And in November 2019, a dog walker was left stunned after stumbling upon on a gun and bullets stashed in a bag in much-loved Liverpool park.
The revolver and ammo found close to a hedge in Croxteth Country Park were later handed to forensic experts after the shocked pet owner made their discovery.