Police have released CCTV footage of the car used by the gunmen who shot senior detective John Caldwell at a sports complex in Co Tyrone last week.
At least 10 shots were fired during the attack, with two hitting vehicles in the car park.
A reward worth up to £20,000 (€22,500) is also being offered by the independent charity Crimestoppers to anyone who has key information about those responsible.
At a press conference in Omagh, Detective Chief Superintendent Eamonn Corrigan appealed to anyone who had seen the car in the two weeks before the attack.
“Today I am releasing CCTV footage of the car used by the gunmen. This is a blue Ford Fiesta, registration number MGZ 6242. It was then fitted with false plates, FRZ 8414, prior to the attack,” Mr Corrigan said.
“Our CCTV footage shows the car leaving the sports complex and turning left on to the Killyclogher Road immediately after the shooting. We then know it travelled past Glendale Service Station to the Racolpa Road where they abandoned the car and set it on fire.
“We have established that the car was purchased in Ballyclare on Wednesday February 8 and was observed travelling towards Belfast on the M2 motorway that night.
“It was next noted leaving Belfast at around 9.30pm on Tuesday February 21 – the night before the attack on John – and travelled along the M1 motorway in the direction of Coalisland/Omagh.
“My appeal today is for anyone who knows where this car was kept in Belfast in the preceding two weeks or anyone who knows where it was stored after it travelled to Omagh on the Tuesday night.”
Detective Chief Inspector John Caldwell has been fighting for his life in hospital since he was shot in front of his young son in Co Tyrone last Wednesday.
He was targeted at a sports centre in Omagh, where he coaches a youth football team, by, police believe, two gunmen who fired multiple shots. As of Monday his condition remains critical but stable.
Police are also reviewing an unverified claim of responsibility by the New IRA.
Last week, the Police Service of Northern Ireland (PSNI) said they believe the attack was terror-related, describing the New IRA as their primary line of inquiry.
Six men, aged 22, 38, 43, 45, 47 and 71, are being questioned in police custody.
Twelve searches in Omagh and surrounding area have also been carried out.
On Sunday night, a typed message appeared on a wall in Londonderry, purportedly from the New IRA and claiming responsibility for Mr Caldwell’s attempted murder.
It was signed by “T O’Neill” – a name previously used by the dissident terrorist group.
It said: “The Irish Republican Army claim responsibility for the military operation targeting senior Crown Force member John Caldwell.
“An active service unit of the IRA were in position to target the enemy within our chosen kill zone with other armed volunteers giving cover.
“All volunteers returned safely to base.
“Irish Republican Army intelligence are now in possession of security information regarding the out of bounds movement of Crown Force personnel.
“We would say this, you still have to try and live a normal life day-to-day, one of these days the IRA will be waiting. T O’Neill.”
On Monday, Assistant Chief Constable Mark McEwan said: “Police are aware of the claim of responsibility.
“We are currently reviewing its contents as part of the overall investigation.
“On Friday, we confirmed that we were treating the attempted murder of DCI John Caldwell as terrorist-related and our primary line of enquiry was the New IRA.”
Mr Corrigan said it is believed that “a number of people” were involved in the attack.
“Quite clearly, this attack was carefully planned and was planned in advance,” he said.
“A vehicle has been obtained weeks ahead of the attack on John, it travelled down the night before on false plates.
“I believe that a number of people were involved in the plan to attack and kill John, they haven’t been successful but there have been a number of people involved in this. It has been carefully planned, it carries all the signs of a terrorist attack that we’ve seen in the past.”
He added: “The PSNI is working closely with our officers to ensure their welfare and wellbeing. We’re also making officers more aware of personal security factors. The fact is, the threat level at the moment is severe, an attack is likely – we have seen that this week.”
On Saturday, people gathered in the village of Beragh and in nearby Omagh to show their solidarity with Mr Caldwell.
