Two explosions in Derry forced elderly residents to leave their sheltered accommodation.
Homes and businesses in the city centre were also evacuated after police received two telephone bomb warnings shortly after 6:30am this morning AEST.
Nobody was injured by the blasts shortly after close to a tourist office and DHSS premises in a busy centre for nightlife and shopping.
Dissident republicans were blamed by politicians.
PSNI district commander in the city, Chief Superintendent Stephen Martin, said his men had acted swiftly.
“The reckless acts of those who planted these devices stand in stark contrast to those of the brave officers who entered these areas to evacuate local residents and businesses,” he said. “The people in Derry do not want this disruption. It is cowardly and callous.”
Next year Derry is the UK City of Culture. Dissidents have targeted the organising committee’s offices before as well as a police station on Strand Road. Thursday’s attacks happened in Foyle Street and Strand Road.
Mr Martin added: “People simply want to move on with their lives, not take a step back. Regrettably the whole community will once again suffer as a result of the needless actions of a few. We will experience major traffic disruption tonight and for much of tomorrow and life will be severely disrupted in the city.”
The area has been cordoned off and forensic examination will go on for much of Friday.
Ulster Unionist leader Tom Elliott said he had no doubt dissidents were behind the attacks. “These attacks further no cause. They will not create a single job or attract a single pound of investment,” he said.
“Londonderry should be enjoying the limelight as the UK City of Culture (next year), yet instead some madmen seem to think it is an opportunity for them to seize some publicity. This type of fascism was part of our past. It has no place in our future.”
Justice Minister David Ford said: “These are the desperate actions of yesterday’s men. They seem to be more wedded to the struggle than to the cause they claim to be pursuing.”