Northern Ireland's police are heightening security in Belfast, deploying roadblocks to deter car bombs, following the first such failed attack on the capital in a decade.

Sunday's 130-pound (60-kilogram) bomb failed to detonate under Belfast's biggest, glitziest shopping center.

Police commanders and security analysts warn that Irish Republican Army splinter groups opposed to a 1997 cease-fire are increasing their bombing efforts in the run-up to Christmas. Several small bombs planted recently in Belfast and Londonderry, Northern Ireland's second-largest city, all have failed to detonate.

Belfast's mayor, a former supporter of IRA violence, says the truce-breakers "want to wreck Christmas." He says Tuesday's crowds of shoppers show "the rest of us aren't going to let them."

Most IRA members from the dominant faction, the Provisionals, renounced violence in 2005.