Armed police seal off part of Belfast after a small explosion in the city centre.

A fire bomb attack on a Belfast shop led to a large security operation in the city centre last Christmas. Pic Arthur Allison

Scene of crime officers after a fire bomb attack on a Belfast shop which led to a large security operation in the city centre. Pic Arthur Allison

A fire bomb attack on a Belfast city centre store represents a serious upsurge by dissident republicans, Northern Ireland's Police Federation warned.

The assailant might have suffered burns to his face, neck and hands after the device exploded as he was about to plant it in a sports shop.

He fled through crowded nearby streets desperately attempting to beat out the flames when the incendiary bomb went off prematurely underneath an anorak-type jacket.

Up to 15 people were inside the pop-up golf store at the time. None was hurt, but the bomber - a man in his mid-40s who was also wearing a beany hat - was engulfed in flames and almost certainly badly injured, according to police today.

Terry Spence, chairman of the Federation which represents rank and file officers, said: "It is deeply worrying and it is a very serious upsurge in dissident republican terrorism."

Dissident republicans are believed to have been involved in the failed attack, the latest in a series in Belfast in the run-up to Christmas.

They tried to blow up an underground car park at the Victoria Centre, the city's biggest shopping centre, and then abandoned a bomb in a holdall in the Cathedral Quarter last Friday night. Up to 1,000 people had to be evacuated from pubs, clubs and restaurants, but only the bomb detonators went off.

Security has been stepped up because of the heightened threat. With three men due in court in Belfast today to face a number of terrorist-related charges - some of them linked to a gun attack on police in north Belfast - checkpoints have been mounted on roads across Northern Ireland.

The remains of the incendiary device recovered last night showed it was the first of this type used by terrorists for some time.

A spokesman for the Federation said: "It certainly represents a change of tactic and is a direct assault on the retail trade at a particularly critical time coming up to Christmas.

"It puts the lives of ordinary people at risk."

Mr Spence said police needed members of the public to come forward with information.

"We are deeply concerned on the basis that we have had 18 bombing incidents in seven weeks and that in itself is a very telling story," he added.

"Most of those attacks have been against police officers on duty and indeed one case of an under-car booby trap device involving an officer who was retired.

"It needs to be dealt with robustly and we are hoping that the community will come forward."

Monday's attempted fire bombing happened at the Golf Madness shop and owner Nick Pierpoint described the incident as "sickening".

He told the BBC: "He (the man) seemed to be flicking at something and, I think, maybe the thing (fire bomb) had gone off and then, literally, he started to go up into flames, which obviously panicked him and panicked us, and he just ran out of the shop and ran down the street,"

Police Service of Northern Ireland (PSNI) Chief Superintendent Alan McCrum said the man may require treatment for burns injuries, to neck, face and hands.

"Police are doing everything to protect Belfast and other places to enable people to go about their business peacefully," he added.