Taoiseach Micheál Martin has said he is "very shocked and deeply saddened" after a member of the Roads Policing Unit was killed in the line of duty.
Garda Kevin Flatley was killed after he was struck by a motorcycle while carrying out a checkpoint in the Lanestown area of north county Dublin.
Speaking in Cork, Micheál Martin said he wanted to extend his "deepest sympathies to his family, to his friends and to the entire membership of An Garda Síochána".
Gardaí work bravely on our behalf to keep us safe every day, he said, and it is "truly shocking" that this has occurred.
President Michael D Higgins said that Gda Flatley "dedicated his career to public service and to keeping people safe".
"The loss of a garda has a deep impact on society due to this strong connection and my thoughts are with his family and all those who knew and cared for Gda Flatley across his life," President Higgins added.
Garda Commissioner Drew Harris said his thoughts were with Gda Flatley's family and friends.
"All the assistance that could be rendered was rendered as quickly as possible."
He said the 49-year-old had "26 years of dedicated service to An Garda Síochána and the people of Ireland".
His death is a "terrible reminder of the dangers faced by gardaí", Mr Harris added.
Gda Flately is the 90th member of the force to be killed in the line of duty, the Commissioner added.
Garda Commissioner renews call for dash-cam footage
Mr Harris said gardaí are particularly interested interested in the movement of a large Yamaha 1000cc motorcycle.
He renewed the call for dash-cam footage, adding that they have "already received a lot of assistance from the public."
The Commissioner thanked the public, other emergency services and an off-duty doctor who "came immediately to the aid of Kevin".
"All the assistance that could be rendered was rendered as quickly as possible," Mr Harris added.
Garda Assistant Commissioner for the Dublin Metropolitan Division said that Gda Flately was "well regarded by his colleagues" and "very much involved in his own community" in Balbriggan.
Paul Cleary added that his death was a "huge loss to our Garda family".
The Tánaiste has said he learned of the death of Gda Flatley with "profound shock and sadness".
In a statement, Simon Harris said Gda Flatley was a "long-serving and much-respected" member of the force.
Minister for Justice 'shocked' at death of Garda Flatley
Minister for Justice Jim O'Callaghan said he is "shocked" at the death of Gda Flatley.
"I know his death will bring heartbreak to his family, friends, loved ones and his colleagues in An Garda Síochána across the whole country," he said in a statement.
"As Minister for Justice, I convey my deepest sympathy and condolences to the parents, family and friends of Garda Flatley and indeed to the whole family of An Garda Síochána," he added.
Minister for Transport Darragh O'Brien described the news as "tragic" in a post on social media.
"My heartfelt thoughts are with their family, friends, and colleagues at this difficult time.
"Anyone with information should contact the Gardaí immediately," he added.
Sinn Féin leader Mary Lou McDonald offered her "deepest condolences" to Gda Flatley's family and colleagues and described the incident as "shocking and heartbreaking".
Sinn Féin's Louise O'Reilly, who is a TD for Dublin-Fingal, said it was an "immensely tragic day" for Gda Flatley's family and friends.
"It's very hard to think that this happened in our community on a bright Sunday afternoon," she said.
"Local people are in shock at this devastating news," Ms O'Reilly added.
The President of the Garda Representative Association has said they are "numbed by the sudden and devastating loss of a colleague, friend and member of the garda family".
Mark O'Meara said that "today our thoughts and prayers are with our fallen member, his wife and children and his family as well as his wide circle of friends and colleagues.
"We have lost a wonderful friend and colleague and he will never be forgotten for what he gave to public service and what he meant to his colleagues," he added.
While, the GRA Vice President has said he and his colleagues have been left numbed and saddened by the death of their "cherished colleague".
Detective Garda Niall Hodgins, who represents the north Dublin Metropolitan Region said: "Not only was he a teammate of the wider Garda family, he was a cherished colleague and a great friend to all of us."
He said Gda Flatley was a young family man "and to his wife and to his children we extend our deepest condolences at this very tragic and sad time".
Det Gda Hodgins also offered his condolences to his friends who served with him in Pearse Street and Blanchardstown Garda Stations.
"Particularly those colleagues of his that work alongside him in the Roads Policing Unit."
He added that Gda Flatley had given great service and dedication to his community and had been working this weekend to try to ensure Irish roads were kept safe.
"This is indicative and a reminder of the dangers that members of the garda face every single day that they go out to perform their duties," Det Gda Hodgins said.
AGSI describes 'dark day' for force
The Association of Garda Sergeants and Inspectors (AGSI) has described the incident as "devastating" and a "dark day" for the force.
General Secretary Ronan Clogher said the AGSI expressed its deepest sympathies to the family and colleagues of the garda that died.
"There will be tough days ahead and we really ask for the public's support."
"We are in shock and numbed at the news this afternoon. No garda shift is ever routine, but this one has ended in the most horrendous of circumstances.
"We extend our deepest condolences to the family, friends and colleagues of the deceased member.
"It is not easy for garda colleagues today so please keep them in your thoughts," he said.
AGSI President Declan Higgins said the association will provide "all their support to members, garda colleagues and their families at this tragic time".
Mr Higgins also urged the public to provide any information they may have about the incident to gardaí.
"I would ask the public to respond to calls for any information as they work on this investigation. There will be tough days ahead and we really ask for the public's support."
The Policing and Community Safety Authority said it was "shocked" by the news of Gda Flatley's death.
"We extend our deepest sympathies to Garda Flatley's family, friends and colleagues," it said on social media.
The PSNI has extended its "heartfelt condolences" to Gda Flatley's family, friends and colleagues.
Chief Constable Jon Boutcher said the "loss of an officer is felt across the entire policing family".
"Kevin's death is a stark reminder of the risks that police officers face every day as they work to protect the public and keep people safe," he said.
"His dedication, service and sacrifice will never be forgotten."
Additional reporting Eleanor Burnhill
