The SDLP has said it believes loyalists were responsible for planting three incendiary devices in Co Antrim. One exploded in the letterbox of a Ballycastle furniture store, causing minor damage. The others were defused.
No paramilitary group has claimed responsibility and the RUC said it was too early to say who was behind the attacks.
However, Mr Sean Farren, an SDLP Assembly member, said: "Given that two of the targets were Catholic-owned businesses and the third was a credit union, it is very difficult to come to any other conclusion than that loyalists were responsible. There has been ongoing loyalist activity in this area."
The device discovered at an off-licence in Ann Street, Ballycastle, was made safe by British army bomb experts. Staff in the credit union offices in Ballymoney spotted the device planted there. It was carried outside where army bomb experts dealt with it.
The North's First Minister, Mr David Trimble, said "any development of that nature is not going to encourage confidence in the peace process". The attacks reinforced his party's concern "about whether the paramilitaries are really committed to progress and really committed to implementing the agreement in the way we would like to".
The Northern Ireland Office was equally reticent about apportioning blame but said the attacks were to be condemned.
The RUC deputy sub-divisional commander leading the investigation, Chief Insp Terry Shevlin, said: "We are not ruling out anything and are keeping an open mind."
The owner of the furniture store, Mr Frank McCaughan, said he had no idea why he had been targeted, only three weeks after opening for business.
He said: "We are closed on Wednesdays and we got a phone call about 11 a.m. saying the shop was on fire. I heard the fire alarm and knew something quite serious was going on.
"My main concern was about the five people living in the premises above the shop. Being a pine shop it could have gone up within five or 10 minutes."
Mr Farren visited the scene of the attacks and condemned them. He asked how trying to burn down a shop or a credit union would further anyone's cause.
The DUP leader, the Rev Ian Paisley MP, said: "No matter who did this, they have to be absolutely denounced and condemned and every effort made to bring them to justice."