A senior police officer was shot by masked men in front of young people he had been coaching at a sports centre in Co Tyrone.
The man, who is senior ranking, was shot a number of times at the facility in Omagh around 8pm on Wednesday. He was taken to Altnagelvin Hospital in Londonderry where Northern Ireland's chief constable Simon Byrne said he was in a critical but stable condition.
The Police Service of Northern Ireland (PSNI) have launched an attempted murder investigation.
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. In a statement, the PSNI said the officer was injured just before 8pm on Wednesday evening.
"One man, a serving police officer, has been taken to hospital for treatment after being injured in a shooting incident at a sports complex just before 8pm this evening," they said.
In a statement on Wednesday evening, the Garda said it is "currently 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," a spokesperson said. "An Garda Siochana has intensified patrolling in border counties."
Mr Byrne said his thoughts are with the injured officer, his family and his colleagues.
"We will relentlessly pursue those responsible," he said. "They have nothing to offer the community."
Ulster Unionist Assembly member Tom Elliott said the officer was coaching young people when the attack took place.
"My understanding is he was coaching young people at a local sports complex and I think they were nearing the end of the session or maybe at the end of the session and there would obviously have been some of these young people around at that time and I am told that two masked gunmen walked up and shot him a number of times," Mr Elliott told Nolan Live on BBC One NI.
"To see that happen in front of you for young people is indescribable almost, and I'm sure will have a lasting impact on them. At this stage clearly we're all thinking of this police officer and his immediate family and we're just hoping and praying that the officer will get better."
Liam Kelly, chair of the Police Federation for Northern Ireland, which represents rank and file officers, branded as "barbaric and cold-blooded" the gun attack in Omagh that has left an officer fighting for his life.
"It's understood two gunmen were involved in the attack. The injured officer was shot a number of times whilst he coached young persons playing football," he said.
"This was a callous, cold-blooded and barbaric attempted murder on an off-duty officer.
"The officer is well known and respected in the area and plays an active role in the community. He is also well known within policing circles and is highly regarded by his colleagues.
"The people who carried out this cowardly and shocking act must be quickly identified and apprehended and I would appeal to the community to assist the police in whatever way they can.
"My thoughts, and those of all police officers, are with our colleague and his family. The police family is strong and resilient, and we'll be there for him and his family in this dreadful hour of need."
The shooting has been condemned by politicians across the UK and Ireland. Prime Minister Rishi Sunak said he was appalled by the "disgraceful shooting of an off-duty police officer in Omagh".
"My thoughts are with the officer and his family," he said. "There is no place in our society for those who seek to harm public servants protecting communities."
Irish premier Leo Varadkar condemned the "grotesque act of attempted murder".
"Our thoughts are with the injured officer, his family, colleagues and friends at this difficult time," the Taoiseach said. "I utterly condemn this grotesque act of attempted murder.
"I call on anyone with information about it to share it with the PSNI."
Sinn Fein vice president Michelle O'Neill said it was an "outrageous and shameful attack".
"My immediate thoughts are with the officer and his family," she said. "I unreservedly condemn this reprehensible attempt to murder a police officer."
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," he said. "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."
Former Stormont justice minister, Naomi Long, said her thoughts were with the officer, his family, colleagues and all those affected by the shooting. The Alliance Party leader branded the attack an "evil act of cowardice".
UUP leader Doug Beattie said: "A man is fighting for his life, supported by our society's finest, our doctors and nurses. I pray he survives.
"There will be plenty to say in the days and weeks ahead about why anyone thinks they have any authority - moral, political or otherwise - to do something as cowardly as shoot a police officer. For tonight, my thoughts are with the officer, his family, his colleagues and those who are looking after him."
SDLP leader Colum Eastwood said the shooting was a "chilling attack".
"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," he said.
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