Bomb disposal experts have carried out a controlled explosion at Fulwood barracks this afternoon.
Army staff called the police for help after a member of public handed in a Second World War hand grenade at 11am.
An Army spokesman said: “At around 11am a member of the public attended the guard room at Fulwood Barracks, Preston, and asked if a grenade he had acquired could be disposed of here.
“Experienced personnel checked the device and placed it in a safe area on the barracks’ sports fields which were then cordoned off.
“The regional Bomb Disposal Unit of the Royal Logistic Corps was then called from its base at Chester and they identified the object as a World War Two ‘Number 36’ or ‘Mill’s grenade’.
“Just after 3pm it was destroyed in a controlled explosion.”
Nobody was injured in the operation.
Lancashire police were in attendance throughout the operation and warned local residents not to panic if they heard a loud bang in the Fulwood area.
The drama is the latest in a series of controlled explosions to take place in the city.
Bomb disposal experts were called to Avenham Park in March when a suspected mortar shell was found.
A member of the public found the object while using a metal detector and it was blown up in a controlled explosion.
Experts said it was quicker to explode the item, given its distance to residential areas, rather than try and remove it.
In May 2015 a discarded grenade was found buried in a field near Avenham Park, but was found to be rusty and inactive.
That came exactly a week after the park had to be closed while experts carried out a controlled explosion of a potentially live mortar bomb that was discovered in similar circumstances near the Old Tram Bridge.