SDLP offices in north Belfast were bombed last night in an attack which a party Assemblyman believes was carried out by the loyalist Ulster Defence Association.
There were no reports of injuries after the explosion outside the offices in the Antrim Road last night.
Mr Alban Maginness MLA said only "the grace of God" and a steel door protected four people who were in his north Belfast constituency office when the bomb exploded.
In a statement late last night the Taoiseach condemned the attack "in the strongest possible terms".
Mr Ahern said it was "clearly an attack on democracy in Northern Ireland".
Speaking at the scene of the attack, Mr Maginness said he believed loyalist paramilitaries were responsible for the blast which took place shortly before 9 p.m.
Four people were upstairs when the explosion took place. Police said none of the four was injured in the explosion, which blew in the office door and caused extensive damage. However, all were believed to be suffering from shock.
One witness said he saw two men leave the device in the office doorway before 9 p.m. "They were going to light the device but every time they lit it, it went out. They were trying to scare us. Then they ran off and about 15 minutes later there was a bang," he said.
Mr Maginness blamed the "callous, cowardly attack" on the (UDA).
He said the UDA was reacting to comments he made following the decision this week to keep Johnny Adair in prison. Mr Maginness said: "I have no doubt that it's linked to Adair. It's a UDA response or an element associated to the UDA."
Other politicians from the area also condemned the attack. Mr Cecil Walker, Ulster Unionist MP for North Belfast, said it was clearly designed to kill or cause serious injury.
Mr Nigel Dodds, DUP MLA, said the explosion was "an attack on democracy and must be deplored by all sides". Mr Gerry Kelly, the local Sinn Fein MLA, urged nationalists to be on their guard against other possible sectarian incidents in the wake of the explosion.
The Minister for Foreign Affairs, Mr Cowen, said the attack "demonstrated a flagrant disregard for the will of the vast majority of people North and South who are firmly committed to the path of peace and reconciliation".