The 26-year-old man was arrested in Dublin city centre yesterday afternoon by armed garda detectives after an alert that he was in the jurisdiction and could be carrying an improvised weapon.
A murder investigation was launched on Monday after Ms Ward (22) was found dead by PSNI officers at her home on Melrose Street in Belfast on October 1.
The suspect is in garda custody and is understood to have been known to Ms Ward.
Sources say he has been in Dublin for a number weeks and was the subject of a garda alert, with gardaí helping the PSNI with its inquiry.
Gardaí were only notified that the man was in the capital this week after they received intelligence that the suspect was seen at a Tesco in Dublin’s south inner city on September 28.
It is understood that he bought credit top-up for a mobile phone at this location and this played a key role in identifying his whereabouts.
Ms Ward was found dead at her home on Melrose Street off the Lisburn Road on October 1, and was last seen almost a week earlier, on September 25. That day she was seen in Dungannon, at Belfast’s Grand Central Station, and near her home.
After receiving information that the murder suspect was in Dublin, officers were advised that the man might be armed with an improvised weapon and that he suffers from mental health issues.
An Garda Síochána continues to work closely with the Police Service of Northern Ireland on this investigation
The investigation into the murder of Ms Ward will now be taken over by gardaí, who will be responsible for preparing a file for the Director of Public Prosecutions (DPP), even though she was not killed in the jurisdiction. Gardaí said in a statement that they have begun a murder investigation in accordance with provisions under the Criminal Law (Jurisdiction) Act 1976.
This allows for suspects to be tried in the Republic of Ireland for alleged offences that happened in Northern Ireland or mainland UK.
The murder suspect cannot be extradited back to Northern Ireland as the authorities there have not yet charged him with any offence, which means the investigation is now being led by gardaí, who announced details of the arrest.
“An Garda Síochána continues to work closely with the Police Service of Northern Ireland on this investigation,” they said in a statement.
The arrest operation in Dublin city centre was led by the Garda National Bureau of Criminal Investigation (GNBCI) which had the suspect under surveillance.
It is understood Ms Ward suffered an extremely violent death at the hands of a man who was well known to her.
On Tuesday it emerged that the young woman had reported to police that she had been the victim of a violent crime in the weeks before her death.
In a statement, the Office of the Police Ombudsman in Northern Ireland confirmed that its investigation has begun and will focus on the PSNI’s response to her report to police.
Ms Ward was the fourth woman to be murdered in the space of just six weeks in Northern Ireland, something the PSNI has described as “simply unacceptable”.