Suspected IRA dissidents and their supporters hijacked cars Monday in working-class Catholic areas of Northern Ireland in a coordinated effort to block roads and threaten police stations, police said. The Police Service of Northern Ireland said it was receiving a wave of reports of vehicles being hijacked by masked gunmen in several parts of Belfast and in the Kilwilkie district of Lurgan, a power base for Irish Republican Army dissidents southwest of Belfast. Some vehicles were being set on fire in roads to disrupt traffic at rush hour, while others were abandoned near four Belfast police stations and on Northern Ireland's major motorway near Lurgan. Police said they were treating all the abandoned vehicles as potential car bombs, although they cautioned this was unlikely. They urged motorists to avoid Kilwilkie and parts of Catholic west Belfast entirely. Monday's upheaval came at the end of a month in which IRA dissidents shot to death two soldiers and a policeman - the first killings of British security forces since 1998, the year of Northern Ireland's peace accord.