Police are investigating links with the conviction of Michael O'Brien

John and Joan Stirland aged 55 and 53, were killed in Trusthorpe on Sunday.

Mrs Stirland's son, Michael O'Brien, is serving life for the murder of a man outside a Nottingham pub.

Police have also appealed for more information on a dark Volkswagen Passat found burning two miles from the murder scene.

At a news conference on Tuesday Det Supt Graham White confirmed the couple died from gunshot wounds but declined to detail how many shots were fired or what sort of gun was used.

O'Brien is serving life for the murder of Marvyn Bradshaw who was shot outside a pub in Nottingham.

Crucial witnesses

Mr White said: "It's too early to say whether these murders are linked with the murder of Marvyn Bradshaw.

"However, what I can say is that I am working very closely with colleagues in Nottinghamshire and some of those colleagues visited and liaised with me in Mablethorpe yesterday."

He said the link was only one possible line of inquiry and he was determined to keep an "open mind" about the killing at such an early stage of the investigation.

The bungalow remains cordoned off

Mr White added: "We have spoken to a number of witnesses who saw a mid-sized, dark coloured saloon car parked close to the murder scene with its hazard warning lights flashing on Sunday afternoon.

"Two men wearing blue boiler suits or overalls were seen in the vicinity of the car and the murder scene."

The car was then driven off in the direction of Sutton on Sea.

A car, believed to be a dark coloured Volkswagen Passat, was found at about 1530 BST on Sunday by fire crews, in a lane just two miles from the murder scene.

This vehicle has now been taken for forensic tests.

"This was a killing which took place in broad daylight, in the middle of the afternoon on a beautiful summer's afternoon, quite clearly some pre-thought and pre-planning gone into that," said Mr White.

Community 'devastated'

He added that the couple had moved to the coast from the Carlton area of Nottingham around April.

He said: "I am still trying to get the full details of why they moved to this area but quite clearly because of the involvement of their son in the murder investigation they felt the need to move away from the Nottingham area to start a new life.

"They were concerned about their own welfare.

The bodies were discovered by police at 2130 BST on Sunday.

Nearby residents said the couple's three young grandchildren had left following a visit the day before the incident.

Local vicar, the Reverend Les Whitfield, said: "Quite a lot of people in the area are pretty devastated, but I think the people of Trusthorpe are a pretty resilient lot and they will certainly come to terms with it.

"The population here is pretty elderly, people come here to retire, people who look after visitors really."