The senior police officer shot in front of his son in Omagh has been named as Detective Chief Inspector John Caldwell as police said the focus of the investigation is on dissident republicans.

Mr Caldwell remains in a critical but stable condition in hospital following the attack at a sports complex in Omagh, in Co Tyrone, on Wednesday evening.

He was shot a number of times at the facility by masked men in front of his son as well as young people he had been coaching.

Detectives said Mr Caldwell had been putting footballs in the boot of his car when two gunmen approached and fired "multiple shots".

He tried to flee but fell to the ground where the gunmen continued to shoot at him. A "brave" member of the public was praised by police for rushing in and providing first aid after the attack.

Mr Caldwell was a high-profile officer who has led a number of major investigations, including taking a leading role in the murder probe following the killing of Natalie McNally in Lurgan in December.

Assistant Chief Constable Mark McEwan told BBC Radio Ulster: "Last night at approximately 8 o'clock at the youth sports centre in Killyclogher Road, Omagh, whilst John was putting footballs into the boot of his car, and accompanied by his young son, two gunmen approached and we believe both have fired multiple shots.

"John has ran a short distance and he's fallen to the ground, and as he's on the ground the gunmen have continued to fire at him.

"That shows the absolute callous nature of this attack in a crowded space where there are children and parents in the vicinity, and we saw many of those young people and children running in sheer terror to get to safety.

"At least two other vehicles have been struck, and again this highlights the callous and reckless nature of this attack."

The Police Service of Northern Ireland (PSNI) have launched an attempted murder investigation.

ACC McEwan said the "primary focus" on the investigation was on "violent dissident republicans".

He said: "The investigation is at an early stage, we are keeping an open mind. There are multiple strands to that investigation.

"The primary focus is on violent dissident republicans and within that there is a primary focus as well on New IRA."

He added: "The threat level at the moment sits at substantial and that means an attack is highly likely.

"That is an ongoing piece of work in terms of supporting our officers and staff and looking at security arrangements."

Baroness Nuala O'Loan, former police Ombudsman for Northern Ireland, said she had hoped “things like this were in the past”.

Speaking on Radio 4’s Today programme, she said: “For the young people who witnessed it for the coaches, their parents ,all those kinds of people, it's a really really traumatic experience.

“We had hoped we saw these things in the past, we had hoped they would never happen again and we know the children, the young people they’ll carry the scar with them, it's not something they will ever forget.”

She added: “There's a serenity to Omagh its a beautiful place and it's awful to think of that serenity being so shattered again by such an awful crime.”

Temporary detective chief superintendent Eamonn Corrigan said: "Our investigation is now underway and I would appeal to anyone who was in the area and witnessed what happened or could help with our enquiries to make contact with police on 101."

Irish police have intensified patrols amid suspicions the gunmen may have fled across the border.

The officer was off-duty when he was attacked just before 8pm.

He remains in a critical but stable condition after being taken to hospital in Londonderry for treatment.

Ulster Unionist assembly member Tom Elliott said the shooting took place "in front of young people at a football coaching session", calling it a “despicable and cowardly action”.

Irish police have confirmed they are working with the PSNI following the shooting.

A Garda spokesperson said the Irish force was “responding to an ongoing incident which took place earlier this evening in Northern Ireland".

"We are working closely in cooperation with our counterparts in the PSNI," they added.

The Northern Ireland Ambulance Service raced to the scene after receiving a 999 call at 8.02pm following reports of an incident in the Slievard area of Killyclogher.

"NIAS dispatched a Rapid Response Paramedic, an Emergency Crew and an ambulance officer to the incident," a NIAS spokesperson said.

"Following assessment and initial treatment at the scene, one patient was taken by ambulance to Altnagelvin Area Hospital."

A statement from Chief Constable Simon Byrne said he was "shocked and saddened" by the incident and vowed the force would "relentlessly pursue those responsible".

DUP leader Sir Jeffrey Donaldson described the shooting as "terrible news from Omagh".

"Our heart goes out to the family of this courageous police officer and to his colleagues. We condemn outright the cowards responsible for this. These terrorists have nothing to offer and they must be brought to justice. We stand with the PSNI."

Northern Ireland Secretary Chris Heaton-Harris condemned the shooting, adding: "Those responsible for such horror must be brought to justice."

Sinn Fein vice president Michelle O'Neill called it an "outrageous and shameful attack".

"This is an outrageous and shameful attack. My immediate thoughts are with the officer and his family” she said.

Micheál Martin, Ireland's deputy prime minister said he was "appalled" by the incident.

"I urge anyone with information to go to the authorities," he said.

SDLP leader Colum Eastwood called the shooting a "chilling" attack.

Mr Eastwood said: "The brutal attack on a police officer in Omagh this evening is a chilling reminder of the horrifying violence that criminal gangs are willing to visit on the people of Northern Ireland.

"In the face of appalling violence that has no place in modern Ireland, their bravery and selfless dedication to service is an enduring reminder that for every individual determined to tear us apart, there are hundreds more committed to defending our peace and all those who live under it."