Four men have been arrested over the New IRA’s car bomb attack on Londonderry court house.
The blast came shortly after 8pm on Saturday when a vehicle exploded on Bishop Street.
The Police Service of Northern Ireland said it was fortunate that no-one was killed or injured.
Dramatic CCTV footage of the incident released by police has revealed how a group of people had walked past the car containing the bomb just minutes before the explosion.
Assistant Chief Constable Mark Hamilton said the New IRA was their main line of inquiry.
Two men in their 20s were arrested in the city in the early hours of Sunday by detectives investigating the explosion.
Later two men, aged 34 and 42 years were arrested in the city.
On Sunday evening, all four were being held in police custody.
“Our main line of inquiry is against the New IRA,” Mr Hamilton said.
“The New IRA, like most dissident republican groups in Northern Ireland, is small, largely unrepresentative, and determined to drag people back to somewhere they don’t want to be.”
Mr Hamilton detailed how a pizza delivery driver was hijacked on Saturday evening, and his car packed with explosives before being left outside the court house on Bishop Street in Derry.
“We believe that some time after 6pm last night (Saturday), in the Quarry Street area of Derry, a pizza delivery driver was hijacked,” he said.
“He had his Ford Fusion car taken off him by at least two armed men.
“Between then and 7.23pm, a bomb was put in that car, driven at least half a mile to outside the court house on Bishop Street and around three minutes later a phone call went in to the Samaritans in West Midlands in England, which was then passed to West Midlands Police who then contacted us.
“In the intervening minutes we had already found the car and started to evacuate the area. At around 8.09pm, the bomb detonated.
“Fortunately it didn’t kill anybody and fortunately it didn’t cause widespread damage, but clearly it was a very significant attempt to kill people in the local community.”
He added they got everyone evacuated “just in time”.
“The bomb detonated just as we were leaving the area and it is only by good grace that local people were not killed,” he said.
Those evacuated from nearby buildings included hundreds of hotel guests, 150 people from the Masonic Hall and a large number of children from a church youth club.
The attack has been condemned by politicians across the Great Britain, Northern Ireland and the Republic of Ireland.
Mr Hamilton said the attack was “unbelievably reckless”.
“Thankfully the attackers failed to kill or injure any members the local community out socialising and enjoying the best of what the city has to offer,” he said.
“The people responsible for this attack have shown no regard for the community or local businesses.
“They care little about the damage to the area and the disruption they have caused.”
Secretary of State Karen Bradley said those responsible would not be permitted to disrupt progress in Northern Ireland.
“The small number of people responsible have absolutely nothing to offer Northern Ireland’s future and will not prevail,” she said.
“Our voices across the political spectrum are united.
“This is intolerable violence and we want to look forward and build a peaceful future for all in Northern Ireland.
“Thank you to the PSNI and emergency services who are working so hard to keep people safe and secure.”
Ireland’s Premier Leo Varadkar described it as “an appalling, reckless and cynical act of terror”.
The Bishop of Derry and Raphoe Ken Good said the attack was an “act of utter recklessness which showed a callous disregard for the lives and safety of local citizens and visitors alike”.
“It defies belief that anyone would place a bomb on a city centre street, early on a Saturday evening, so close to people’s homes, churches, a hotel, sheltered accommodation, nearby pubs and a large car park.
“St Columb’s Cathedral and St Augustine’s Church, where a group of young people had been meeting yesterday evening, have both had to cancel their Sunday morning services while the police carry out a follow-up security operation,” he said.
“I am extremely thankful that no one was injured, or worse, as a result of last night’s explosion.
“The attack was wrong. It is indefensible. It should never be repeated.
“The time has long since passed when such violence should have been consigned to history.”
The mayor of Derry John Boyle challenged those responsible to explain themselves.
“I would actually like to ask the people responsible for this what it actually was that they thought they were going to achieve.
“It achieves nothing, it didn’t achieve anything in the past, it didn’t achieve anything right now,” the SDLP mayor said.
“This is the past and it has to stay in the past. We don’t want to see any more of it.”
Alternative arrangements have been put in place for cases that had been due to be heard at the Courthouse in Bishop Street.
Crown Court trials with juries have been adjourned until Tuesday while all other Crown Court business, non-trial and jury business, will be dealt with at Coleraine Courthouse on Monday.
Magistrates’ court business will be dealt with at Strabane Court No 1, and County Court equity business will be dealt with at Strabane Court No 2 on Monday.