Officers from Sefton targeted team were on patrol at about 2.30pm this afternoon when they spotted the three men in the alleyway at the rear of houses on Beatrice Street and Benedict Street.
As the officers approached the males, who were all wearing dark clothes with their hoods pulled up, they ran off.
Officers gave chase, and one of the arrested men was seen to throw a black bag over the wall of a property.
Two of the three men were arrested and the bag was recovered along with a Glock handgun, a gun magazine and a number of bullets.
Detective Chief Inspector Sabi Kaur of the Firearms Investigation Team, said: “The force is committed to tackling those involved in serious organised crime, particularly those involved in gun crime, and has dedicated significant resources into taking weapons and offenders off our streets.
“This is a significant recovery of an extremely dangerous weapon and as a result our streets are safer today.”
Both men, a 20-year-old of no fixed abode, and a 28-year-old man from Kirkdale, who were arrested on suspicion of possession of a firearm have been taken to a police station where they will be interviewed by detectives from the Firearms Investigation Team.
Anyone who witnessed the incident, or has any CCTV or dashcam footage is asked to contact @MerPolCC, 101 quoting ref. 20000531299 or Crimestoppers, anonymously on 0800 555 111.