Dissident republicans have been blamed for a series of arson attacks which destroyed major retail premises near the Irish border today.
Security chiefs are investigating the possibility some sort of incendiary devices started the fires which swept through shops in Newry city, Co. Down in the early hours.
Today marks the 35th anniversary of the introduction of internment - once one of the most emotive dates in the republican calendar - when hundreds of men were arrested in nationalist areas and detained without being formally charged.
Damage is expected to run into tens of millions.
Sinn Fein and Ulster Unionist representatives said republicans opposed to the leadership of Gerry Adams and Martin McGuinness were likely to have been involved.
Homes were evacuated as fire swept through Carpetright and MFI stores in the city's Damolly Park area.
At the same time a JJB sports shop was gutted in a blaze a mile away on Merchants Quay. A nearby TK Maxx store suffered heat damage.
Nearly 150 firefighters and 26 fire appliances were brought in during the emergency.
Police urged all businesses and keyholders in the city to check their premises.
They were also examining a security alert on the Belfast-Dublin rail line at Newry.
As the blazes were brought under control Group Commander Walter Johnston confirmed they were probably started deliberately by fire bombs.
"It would be most unusual to have this type of incident at the same time involving four premises," he said.
"As soon as the buildings cool down we will be going through them and police will be helping us.
"We are almost certain they were malicious fires, but how they actually started we are not sure yet.
"The buildings were totally secure when the fire crews arrived."
Ulster Unionist Danny Kennedy, a member of the suspended Northern Ireland Assembly said: "People are completely appalled, shocked and stunned. Undoubtedly it was caused by republican dissidents, and it may well be linked to the anniversary of internment.
"These are multi-national businesses and its important everything possible is done to make them stay in Newry."
Davy Hyland of Sinn Fein said the attacks looked like the work of dissident republicans.
He added: "There is very, very little if any support for what happened. Newry has been through difficult times, but in recent years its gone through a resurgence. Jobs are now in danger of being lost."
The SDLP in Newry claimed up to 60 jobs could be lost because of the destruction.
Dominic Bradley, also a member of the suspended Assembly said: "This type of wanton destruction of property and jobs only underlines once again the utter futility of violence."
The Mayor of Newry and Mourne Michael Carr said there was a tremendous sense of shock and disbelief in the city.
"The people of the city thought that we had put this type of thing behind us," the SDLP mayor said.
"It is clear that no cause can justify this type of destructive and futile action.
"Thankfully no one was injured in last night's fires but there is obvious concern at the huge number of jobs that have been put at risk."
He also paid tribute to firefighters and vowed the city would pull together to ensure Newry recovered and potential investors were not put off by what he described as a few unrepresentative faceless thugs.
"There is a clear sense of defiance in Newry this morning," he observed.
"The city has recovered from worse in the past. It will recover and come back stronger after this."Reuse content