Veronica Wilson appealed for help in catching her husband's killer

Veronica Wilson, 33, made the plea during a media conference at Northern Constabulary headquarters in Inverness on Thursday.

Earlier, about 200 people attended a memorial service at St Ninian's Church in the Highland town.

Police are still hunting the killer of Mr Wilson, 30, who died on 28 November.

The family has not been able to bury Mr Wilson as his body is still being held while police continue their investigations.

I see Al's picture every day, I hear he's murdered, but it's still all so unreal Veronica Wilson

Mrs Wilson and the couple's two young sons have been living under armed guard at a secret location since the shooting.

The minister the Reverend Tony Livesey told reporters there were very few tears in the church and paid tribute to Mrs Wilson who, he said, was brave enough to shake hands with everybody attending as they left.

Mrs Wilson faced journalists at Northern Constabulary's to read a prepared statement.

Her life with her children has been an emotional roller coaster since the murder just over three weeks ago - and she said the question of who and why will continue to haunt them.

Mystery gunman

Occasionally close to tears, she said: "I see Al's picture every day, I hear he's murdered but it's still all so unreal.

"It's just a small step forward to have met close friends, colleagues and neighbours today."

And she appealed once again to anyone who knows anything to come forward. "They need to," she said.

"For the sake of my two young boys we need to find out who and why. So if anyone has any information then please come forward."

Mourners at the service included Detective Inspector Peter MacPhee, the officer leading the murder inquiry, and his deputy Gordon Greensleeves.

Journalists were asked to stay away from the memorial.

Mr Wilson died after being shot three times by a mystery gunman.

A film of Alistair Wilson with his family was shown on Crimewatch

The suspect was described as being aged 35 to 40-years-old and was wearing a baseball cap and a dark blouson jacket.

Three weeks on from the killing, Northern Constabulary have yet to establish a motive.

Detectives confirmed last week that a handgun found in a drain near the scene was the murder weapon.

The case has featured on the BBC's Crimewatch television programme.

Police said that the appeal had prompted a number of interesting calls.

Crimestoppers has offered a �10,000 reward for anyone with information leading to the arrest, charge and subsequent conclusion of the case.