Two 20-year-old suspects were arrested this morning and two other men, aged 34 to 42, were arrested overnight in the city, Northern Ireland police said.
Police have posted several videos on Twitter, one of which shows a person running away from the parked car. In a second video, you see a group of people passing near the vehicle a little before the explosion. A third video shows the explosion, with the debris projected into the air and the car devastated by the flames.
Investigators believe the "new IRA", a dissident arm of the IRA, will be behind the attack.
"Our main clue is the" new IRA "," Deputy Chief of Police Mark Hamilton said at a press conference in a "small group".
The vehicle exploded on Saturday shortly after 8.00 pm in the city center near the courthouse.
"Around 7:55 pm, Bishop Street police detected a suspicious vehicle and was conducting audits when, about five minutes later, we received information that a car was abandoned in court," said Mark Hamilton, police statement. cited by AFP.
The police immediately began to withdraw people from nearby buildings, including hundreds of hotel guests and a large number of children from a youth club in a church.