Dissident republicans have been blamed for firebomb attacks on a number of stores in Belfast.
An incendiary device was left at the Homebase store in Belfast
The Homebase store on Boucher Road was destroyed in one attack, while nearby Smyth's toystore was also targeted. That blaze was brought under control.
JJB Sports in Anne Street in the city was badly damaged a third attack. Tony Blair has condemned the attacks.
NI Secretary Peter Hain said it was an attempt by dissident republicans to derail the St Andrews Agreement.
"They will not be allowed to succeed. We will hunt them down and the whole community is united against them," he said.
The prime minister said: "The best response to such acts of violence is to make sure that the St Andrew's Agreement is fully implemented, that we get the institutions back up and running and that the peace process thrives."
The firebomb attacks came ahead of a meeting between the Northern Ireland political parties and Chancellor Gordon Brown in London on Wednesday about a so-called "peace dividend".
Fire crews were called to all three incidents at about 0200 GMT on Wednesday.
At its height, more than 70 firefighters attended the blaze at the Homebase store, which also spread to Reid's furniture store next door.
A number of staff were in the Homebase store when the device exploded, however, there were no reports of injuries in any of the incidents.
Keyholders in both areas have been asked to check their premises.
Superintendent Ken Eccles said: "We cannot rule out the possibility of more attacks and in light of that I would ask people to be vigilant and also to maintain searches of their premises."
In a statement, Homebase said none of its staff would lose their jobs.
"Our immediate priority is to ensure the well-being of our colleagues involved in last night's incident and we have staff on the ground to offer them advice and counselling," said the company.
"We can also confirm that no colleagues will lose their jobs as a result of this incident."
Divisional Officer Chris Kerr from the Fire Service said the blaze at Boucher Road was very dangerous.
"The crews were deployed inside Reid's and we had aerial appliances pumping water above the premises to stop that fire from spreading," he said.
"At one stage, there was an explosion involving gas cylinders inside the Homebase area, which hampered firefighting efforts.
JJB Sports in Ann Street in the city centre was badly damaged
"But again, all credit to those firefighters - their courage and professionalism resulted in the fire being confined to the Homebase store.
"Although, it has been very, very badly damaged."
Last month, dissident republicans were blamed for a fire bomb attack on a B&Q store in Coleraine.
The Real IRA was also blamed for a series of incendiary attacks on commercial premises in Newry in August.
Belfast city centre manager Joanne Jennings said businesses would not allow the firebombers to defeat them.
"It is a major disappointment for the city, particularly as we have been working all so hard to try and make the city more attractive for investors and people coming in who want to shop," she said.
The chairman of the Belfast District Policing Partnership, DUP councillor Robin Newton, said the attacks were "despicable and senseless".
SDLP MP for South Belfast Alasdair McDonnell said the perpetrators had "nothing to offer society".
Sinn Fein South Belfast assembly member Alex Maskey said the firebomb incidents were "an attack on the peace process".
Meanwhile, police have arrested a 39-year-old man as part of an investigation into dissident republican crime, including incendiary attacks.
Detectives from the crime operations department are carrying out a series of searches on premises at four locations - two in Glengormley, one in Newtownabbey and one in Killough in County Down.
The suspect is being questioned at Antrim police station about dissident activity stretching back over a period of time, a spokesperson said.
A senior detective has been appointed to co-ordinate the police investigation into incendiary attacks.
It is understood the officer had already been given the job prior to Tuesday night's attacks.