Four men are currently being questioned by detectives investigating Saturday night’s car bomb in Derry city centre.
Detectives leading the investigation into the explosion outside Bishop Street courthouse confirmed on Sunday night they had arrested a further two men.
The men aged 34 and 42 were arrested in the city on Sunday evening.
The arrests came hours after two men aged in their 20s were also arrested in Derry on Sunday morning.
Hundreds of hotel guests, 150 people attending an event in the Masonic Hall opposite the courthouse and children from a local church youth club were among those evacuated by police prior to the detonation of a car bomb in the city centre on Saturday evening.
Assistant Chief Constable Mark Hamilton said on Sunday: “At around 7.55pm last night officers on patrol in Bishop Street spotted a suspicious vehicle and were making checks when, around five minutes later, information was received that a device had been left at the courthouse.
“At this stage it appears as though the vehicle used had been hijacked from a delivery driver in the Quarry Street a short time before the explosion.”