Post-mortem due on prison officer Adrian Ismay who died after bomb attack

Adrian Ismay, 52, suffered leg injuries when the booby trapped device detonated under his van in East Belfast on March 4.

Dissident republican group the New IRA, which opposes the peace process, said it was responsible.

The father of three was said to be recovering well but was taken back into hospital on Tuesday morning and died.

It is believed he may have suffered a heart attack.

One man has already been charged with attempted murder but the Police Service of Northern Ireland (PSNI) said detectives will await medical evidence before deciding whether to launch a murder investigation.

The results of the post-mortem are expected later in the day.

Meanwhile, Sue McAllister, director general of the Northern Ireland Prison Service, said she would not be shocked by claims that some paramilitary inmates at Maghaberry high-security jail cheered, smoked cigars and mocked warders when news of Mr Ismay’s death filtered through.

Speaking on BBC Radio Ulster, she said: “That type of thing would not be surprising. But it would be inappropriate to comment until I have validated that for myself.

“Clearly that sort of behaviour is completely unacceptable and it is in stark contrast to the quiet bravery and courage that is being shown by Adrian’s family at this very difficult time.

“We know that a number of prisoners in one part of Maghaberry demonstrate challenging behaviour on a daily basis towards our staff so this would be something we are quite used to dealing with and we will deal with it appropriately.

“Prisoners do have access to tobacco through the tuck shop, but until I have spoken to somebody who actually saw that, it would be too early to comment further.”

Ms McAllister has requested an updated assessment of the level of threat posed by dissident republicans, which has been severe for some time.

Steps have also been taken to remind staff about safety precautions, she added.

“We have reminded staff about the use of social media, about the things they can physically do. We do make availability of staff to put security in their homes,” said Ms McAllister.

“But the important thing is that we have a job to do and we do that job professionally.

“We are working very closely with the PSNI to identify whether and where and when any threats take place and we will be working to keep our colleagues informed.”

Following the attack on Mr Ismay, police commanders warned that violent dissidents were trying to escalate their activities to mark the centenary of the 1916 Easter Rising - a pivotal date in the republican calendar which sparked a series of events that led to 26 counties in Ireland gaining independence from Britain.