Adrian Ismay, who was 52 and a father of three, was seriously hurt after a booby-trap device exploded under his van in Belfast on 4 March.
"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."
"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."
"I am shocked and saddened to hear of the death of this prison officer.
"My thoughts and deepest condolences are with his family."
"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."
"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."
"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 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."
"The people responsible for this despicable attack must be brought to justice.
"I would again reiterate that the people responsible do not represent wider society. They cannot and will not be allowed to take this society back to the past."
"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."
"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."
"Platitudes from the great and the good no longer represent the deep feeling and the hurt of public opinion.
"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."
"As I previously said, 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."
"The attack which led to his death is a stark reminder of the fragility of the peace process in Northern Ireland, and must be condemned in the strongest possible terms.
"This married father of three was a committed public servant who was senselessly targeted by a group determined to destabilise a process which had brought about an end to decades of violence across the north."
Politicians have been reacting to news that a prison officer injured in a bomb attack in Northern Ireland earlier this month has died.