Belfast: A bomb exploded at a civic office in the centre of Londonderry in Northern Ireland on Wednesday night, police said, but no casualties were reported.
Army bomb disposal experts were dispatched to the site within the ancient city walls but the bomb exploded before they could defuse it, a police spokeswoman said.
The office houses the organising committee for Londonderry`s term as UK City of Culture in 2013.
In January, a group of Irish nationalist militants claimed responsibility for another bomb explosion at the same office.
Some Irish nationalists, who want Northern Ireland to be part of a united Ireland, have opposed the awarding of the title UK City of Culture to Londonderry for 2013 -- an award likely to bring in significant investment and tourism.
A 1998 peace agreement largely ended more than three decades of violence between mainly Catholic Irish nationalists and predominantly Protestant unionists who want the province to remain British.
However, dissident nationalists opposed to the deal and seeking a united Ireland fight on with sporadic gun and bomb attacks, which have intensified in the past couple of years.