A cyclist carried a bomb into a city’s busy nightlife area in a holdall on his handlebars, police said.
A pressure cooker was used as part of the device that exploded as Belfast’s Cathedral Quarter was packed with pre-Christmas revellers last December, an investigating officer said.
The PSNI has released two security camera images of the suspected bomber.
A warning had been given but the device was left at a different location from that named in a call to a newspaper.
Police were clearing crowds from several premises when it exploded, disrupting around 1,000 people’s night out.
PSNI Detective Inspector Chris Wilson said: “The attack ruined a night out for hundreds of people but it had the potential to injure or kill.”
Dissident republicans opposed to the peace process were blamed for the attack, part of a series of festive season incidents targeting the city centre which saw the return of police checkpoints and guards outside shopping centres.
The quarteris a popular night spot, partly pedestrianised with its old cobblestone streets full of restaurants and bars.
That part of the city is modern and trendy, a symbol of Belfast’s emergence from conflict, but the explosion produced scenes reminiscent of the past.
Party-goers enjoying Christmas dinners were interrupted by armed police arriving in restaurants warning people to get out as quickly as possible.
Some took their turkey dinners with them and ate in the cold outside.
The bomb was left in a holdall near a popular restaurant in Exchange Street.
Police have released two CCTV images of a man on a bicycle in Talbot Street and Anne’s Square who they believe to be the person who left the holdall containing the bomb.