The PSNI have arrested four people in relation to the attempted murder of a prison officer in Belfast on Friday.
Three men aged 34, 41 and 45 and one woman aged 34 were arrested today. They are currently being questioned by detectives at a Belfast station.
The 52-year-old long-serving prison officer, who is married with children, required surgery after an explosive device detonated under the van he was driving in Belfast on Friday morning.
The explosion occurred in the Hillborough Drive area off the Woodstock Road in the east of the city.
The prison officer is based at Hydebank Wood Young Offenders Centre in south Belfast and works as a trainer for new recruits to the NI Prison Service.
Following the attack, police commanders expressed fears it may be the first of a number of dissident republican murder bids launched to mark the centenary of the Easter Rising.