Dissident republicans have been blamed for a car bomb attack in the North early today.
No-one was injured in the blast in Culmore Road, Derry, but several business properties were damaged.
The bomb, which had been left in a Vauxhall Corsa, went off an hour after a telephone warning by the terrorists.
The worst of the damage was at Ulster Bank and the nearby Da Vinci's hotel and restaurant complex.
Residents in a nursing home and houses in the area had been evacuated before the explosion just after midnight.
Two months ago a 200lb car bomb exploded outside a police station half a mile away in the city's Strand Road. Dissident republicans were also blamed for that explosion.
Police warned of massive traffic disruption in the city today because of a follow-up security operation.
SDLP Mayor Colm Eastwood, who visited the scene, said he was disgusted by the attack.
He said: "I do not know what these people are hoping to achieve. They say they love their country but they spend their time trying to destroy it.
"The people of this city will be very angry.
"It is just shocking that someone would put a bomb anywhere, but especially at a commercial centre."
Yesterday, police chiefs warned of a increasing number of bomb-making techniques employed by dissident republicans, saying the development was of great concern.
There was also increasing co-operation among the renegade groups opposed to the North's peace process, officers from both sides of the border said.
Police Service of Northern Ireland Assistant Chief Constable Judith Gillespie said they were concerned about a "growing capability" of dissident groups.
She said: "We have seen an increase in technical expertise and the successful detonation of improvised explosive devices, the range of techniques they are now using - and that is of great concern.
"And we have also seen groups working more closely together than we have seen in the past and that's also of serious concern."
Dissidents have been responsible for a number of car bomb attacks against security force targets in the North this year.
Mrs Gillespie's warning came weeks after the security services raised the threat level of a dissident attack in mainland UK from moderate to substantial.
Some people in Derry believe the bombing was timed to coincide with a visit to the Conservative Party conference later today by Sinn Féin Deputy First Minister Martin McGuinness, who lives in the city.
Former US president Bill Clinton visited Derry last week.