One Berretta nine-millimetre firearm fitted with one magazine containing 11 rounds of ammunition was found and seized by officers whilst on mobile patrol in the Western Division on Sunday.
Police also seized one additional magazine with 33 rounds of nine-millimetre ammunition.
While proceeding north along the North Post Road around 9:30 am, officers observed a man walking in the direction of the motor vehicle.
The man appeared to be of mixed descent and approximately 5ft 6 inches tall.
Upon seeing the marked police vehicle, the man dropped a blue knapsack which he was carrying and ran away.
The officers seized the knapsack which landed on the northern side of the drain.
They chased the suspect but he escaped into the nearby bushes.
A check of the knapsack was made and the firearm and the ammunition were discovered and seized.
Investigations are continuing.