An office involved in planning Derry's term as UK City of Culture was the apparent target of a bomb attack today.
Officials said the building's front door suffered minor damage in an explosion in Derry city centre, believed to have been caused by a small device at around 3.30am.
Police sealed off the Custom House Street area and launched a security operation following the blast.
The pedestrian area in Guildhall Square, which last year was the scene of the release of the Saville report into Bloody Sunday, was also closed off.
Police have yet to confirm details.
But Mayor Colum Eastwood said minor damage had been caused to the City of Culture office, which he described as an attack on the people of Derry.
SDLP Assembly member for the area Pol Callaghan said: "This is more than an attack on a building - it is an attack on the rebirth of our city and our hopes for the future. It will not succeed.
"The wider community wants progress, not a return to the dark days of the past."