David Cameron 'saddened' by Adrian Ismay death and sends his condolences to family
"Deeply saddened to hear prison officer injured in bomb attack in Belfast on March 4 has died. Thoughts with father-of-three's family."
Prime Minister David Cameron
"I am personally devastated to hear this news this morning.
"Of course what we must do is support [ Chief Constable] George [Hamilton] and his colleagues to make sure that those who tried to murder this man are brought to justice
"I had been in touch with this prison officer after his trauma and he had indicated that he was doing well and it is just so, so sad to hear this morning that he has passed away."
First Minister Arlene Foster
"I'm deeply saddened that this prison officer has lost his life.
"Obviously first and foremost my thoughts and prayers are with his wife and three daughters
"These are futile acts that will achieve absolutely nothing."
Deputy First Minister Martin McGuinness
"I am shocked and saddened to hear of the death of this prison officer.
"My thoughts and deepest condolences are with his family."
Northern Ireland Secretary Theresa Villiers
"Adrian Ismay gave over 28 years of service to prisons in Northern Ireland and he was greatly respected by all those who knew him.
"Our thoughts and prayers are with his family, friends and colleagues at this difficult time."
Justice Minister David Ford and Prison Service director-general Sue McAllister
"We must continue to work at all levels to copper fasten a future for Northern Ireland that is committed to the democratic process and the rule of law and is free from violence and intimidation."
Taoiseach Enda Kenny
"A very sad day indeed for Northern Ireland and for everyone who wants to see progress and peace continue.
"Yet another family unnecessarily traumatised and grief brought to bear upon them as a result of people using violence in this way, which is just entirely inexcusable."
PSNI Chief Constable George Hamilton
"In offering my deepest sympathy and condolences to them, I pray that they would know God's love and comfort at this intensely difficult time."
Presbyterian Moderator, Rev Dr Ian McNie
"I am deeply saddened by the death of Prison Officer Adrian Ismay and wish to express my sincere and heartfelt condolences to his family. I pray that they would be deeply aware of God's grace, consolation and blessing, and ask for continued support for them in prayer in the days that lie ahead. The attack on Prison Officer Ismay was a deplorable and terrible act.
"I commend all those who serve in the Northern Ireland Prison Service on behalf of our community. They deserve our fullest support."
Rt Rev Harold Miller, Church of Ireland Bishop of Down and Dromore
I was shocked upon receiving the tragic news of the death of Mr Adrian Ismay. I extend my deepest condolences and my prayerful support to his family in their grief and to his colleagues within the Prison Service at this extremely difficult time.
As a society, let us be more determined than ever to work for peace and for the good of each other. The future of Northern Ireland can only find its foundation in community engagement and political dialogue rather than through the senseless and destructive pursuit of violence.
Noel Treanor, Catholic Bishop of Down and Connor Noel Treanor
"I am devastated to hear of the death of prison officer Adrian Ismay.
"My thoughts are with his family and friends and all who put on a uniform to keep us safe.
"Whatever the exact cause of death, I cannot accept he would be dead if it were not for the bomb.
"Those with knowledge of the perpetrators must come forward."
Ulster Unionist Party leader Mike Nesbitt
"News of the death of Adrian Ismay, a prison officer who was targeted in a bomb attack in east Belfast last week, is a huge blow to all of us who have stood against those with such murderous intent.
"My thoughts and the thoughts of the SDLP are with Adrian's family and friends at this very difficult time.
"Violent dissident republicanism has declared its intent to escalate a campaign of murder and mayhem. Today we must all make a declaration of our intent to escalate our response. We will not be bullied, we will not be dragged back and we will not be broken.
SDLP leader Colum Eastwood MLA
"I am stunned and deeply saddened to learn that the prison officer from my constituency has passed away.
"It will not just be the people of east Belfast who share in this grief, but also everyone in Northern Ireland.
"Mr Ismay has lost his life at the hands of terrorist murderers simply because he chose a career working in the service of our community. He was not just a brave and dedicated prison officer, but most importantly he was a loving husband and father."
Gavin Robinson, East Belfast MP
"You will have many of the critics of the peace process on the airwaves during the year and then once an attack takes place where somebody is killed or severely injured they disappear. They need to come out, they need to explain themselves and they need to be open to challenge."
Sinn Fein MLA John O'Dowd
"It was thought that he was making a good recovery.
"I don't know what he suffered but he's dead and it is very hard to come to terms with."
Finlay Spratt, chairman of the Prison Officers' Association
"Adrian was the father of three grown-up daughters and had over 28 years' service with the Prison Service.
"He was greatly respected by all those who knew him.
"Our deepest sympathy is with Adrian's family, friends and colleagues at this sad time."
Detective Chief Inspector Richard Campbell
"We need action now to round up for whatever reason all those people that the security forces believe would make us safer if they were no longer roaming and able to take innocent lives."
Ukip leader in Northern Ireland David McNarry MLA
"This was a callous and cowardly attack on the entire community.
"We must work together to reject those who would wish to return Northern Ireland to the days when these heinous attacks were commonplace. Their futile agenda will not succeed. We best honour Adrian's memory by redoubling our efforts to build a truly peaceful future for the people of Northern Ireland."
Irish Foreign Affairs Minister Charlie Flanagan
"I am devastated at this news and my thoughts are with Mr Ismay's family.
"Violence is never the answer and I utterly condemn this mindless, needless attack."
Steven Agnew MLA, Green Party
"Our hearts go out to Adrian Ismay's family.
"They will be experiencing the dreadful pain of loss, and I know they will have the support of the extended family circle, Prison Service colleagues and of course the wider community.
"He was doing an essential job for this entire community when dissident republicans singled him out. The plain and simple truth is that there can never be any justification for such cowardly actions.
"A man's life is lost for a futile cause and a whole family is plunged into grief."
Mark Lindsay, chairman of the Police Federation for Northern Ireland