Four men have been arrested by detectives investigating a car bomb that exploded outside Bishop Street courthouse in Londonderry.
Police believe a pizza delivery driver was hijacked by at least two armed men in the Quarry Street area shortly after six o’clock on Saturday night.
A bomb was put in the Ford Fusion car before being driven to the courthouse on Bishop Street at around 19.20 pm.
Police have described the attack as a ‘significant attempt to kill’.
Two men, who are both in their twenties, were arrested in the city on Sunday morning. Two more men, aged 34 and 42, were arrested in the city on Sunday evening.
A warning was called into the Samaritans in England at around half-past seven on Saturday night. It was diverted to the West Midlands police who made the PSNI aware of the call.
The car was located and officers evacuated the Bishop Street area.
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.
PSNI Assistant Chief Constable Mark Hamilton said the area was cleared "just in time".
Earlier fears of a secondary device have been ruled out.
PSNI Assistant Chief Constable Mark Hamilton told media at a press conference at the scene on Sunday that their main line of inquiry was that the dissident republican group, the New IRA, were behind the car bomb attack.
"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."
He continued: "This (investigation) is primarily focused upon local people in this city attacking their own city.
"This device hasn't been as effective as they would have wanted it to be they haven't killed anybody and they haven't created widespread damage."
Northern Ireland Secretary of State Karen Bradley has said those behind the bomb attack will not prevail.
"This attempt to disrupt progress in Northern Ireland has rightly been met with utter condemnation from all parts of the community."
She continued: "The small number of people responsible have absolutely nothing to offer Northern Ireland's future and will not prevail.
"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."
The Taoiseach Leo Varadkar said his government condemns the incident in the "strongest possible terms".
Commenting on social media he said: "This was an appalling, reckless and cynical act of terror.
"Violence to achieve political objectives has been rejected by the people of this island again and again."
Alternative arrangements have been put in place for cases that had been due to be heard at Bishop Street courthouse on Monday.