Spanish police say a gun potentially used to kill Irish journalist Veronica Guerin had been hidden "like a souvenir" in the garden of a drug baron's Costa Blanca villa.

Detectives conducted a raid on the home of infamous Irish criminal John Gilligan this week and found a gun of the same make and model as the one used to murder Ms. Guerin in 1996.

They say the Colt Python .357 Magnum seized from Gilligan's home in Torrevieja, near Alicante, is very rare - although it will take "months" to determine whether it is the murder weapon.

Ms Guerin was working for the Sunday Independent when she was shot dead at a red traffic light on the Naas dual carriageway on the outskirts of Dublin 24 years ago.

The gun used in her killing was never found.

The crime led to Gilligan's trial and acquittal for masterminding her murder and a 28-year prison sentence for importing two tonnes of cannabis resin worth £32m.

He has always denied involvement in the murder.

One well-placed Spanish source said: "On one hand, it wouldn't make sense for Gilligan to keep the murder weapon at his home because it would incriminate him. But this gun was not being kept to use, quite the contrary.

"It had been hidden by someone who had placed the gun in a hole they dug in the ground and covered with gravel and a type of cloth you use to stop weeds coming through before more gravel was piled on top.

"Normally criminals keep their guns in places they can easily reach them like a bedside drawer but this one was being kept as if it were a souvenir by someone who didn't want to part company with it, outside rather than inside where it could easily be found."

Another insider said the .357 Magnum is a "very large, cumbersome revolver which is not easy to hide and the sort of weapon you see very rarely".

One highly experienced Spanish officer specialising in fighting organised crime revealed he had only seen two guns of the type confiscated from Gilligan's garden in the past 20 years.

"It will take months for the police involved in this case to determine whether or not the weapon was used to kill the Irish journalist," he said.

"Spanish police will already be in contact with Garda and they will obtain the projectiles recovered from Veronica Guerin's autopsy.

"Each weapon is unique, just like a fingerprint and when you fire off a cartridge you leave micro identifications which are characteristic of a specific weapon and in ballistics differentiate one projectile from another and one weapon from another."

He added the fact the gun was so rare made it "very possible" it is the murder weapon.

Well-placed sources said the raid on the drugs baron's villa took place as he was preparing a delivery to Ireland of marijuana and prescription-only powerful sleeping pills.

Gilligan has not yet been formally charged with any crime as charges are only laid shortly before trial in Spain, but he is in custody along with five other suspects for crimes against public health, unlawful possession of firearms and membership of a criminal gang.

Former friend Brian Meehan was convicted of Ms. Guerin's murder in 1999 and remains in prison.