Bomb Found in Northern Ireland on Eve of Clinton Visit LONDON - After days of sectarian unrest in Northern Ireland, four men were arrested late on Thursday after a homemade bomb was found in the city of Londonderry, police officials said, coincidentally on the eve of a visit to the province on Friday by Secretary of State Hillary Rodham Clinton. The tensions are not seen as being related to Mrs. Clinton's visit, analysts said, but offer a sobering backdrop to what has been depicted as a celebratory visit recalling President Bill Clinton's diplomatic triumphs in securing the Northern Ireland peace. Both the former president and Mrs. Clinton command broad popularity in Northern Ireland, a factor that weighs with Irish-American voters in American politics. Police officials said the bomb was found in a car by officers investigating the activities of splinter groups who have broken away from the mainstream Republican movement to oppose British sovereignty in Northern Ireland. Two men were arrested when the bomb was discovered and two more were detained later, the police said. The explosive device was described by the police as "viable." Army experts defused the bomb after nearby homes were evacuated. Reporters in Northern Ireland said dissident Republicans were opposed to the designation of Londonderry as a United Kingdom City of Culture in 2013. The name of the city is disputed, with the predominantly Roman Catholic majority referring to it as Derry, its name before British authorities changed its name to Londonderry centuries ago. Last month, a prison officer, David Black, was shot dead in Northern Ireland and a republican splinter group said it carried out the killing to protest conditions at a jail where guards carry out strip searches on detained republican dissidents. The discovery of the device on Thursday came after days of protests by unionist groups, which support continued ties with Britain, against a decision to restrict the number of days when the British Union Jack flag is flown over Belfast City Hall. Those protests have spread to other parts of Northern Ireland, illustrating the enduring power of sectarian passions years despite the 1998 Good Friday agreement that cemented peace after 30 years of conflict, known as The Troubles, in which more than 3,500 people were killed. British news reports said Mrs. Clinton is to address lawmakers and visit a new center devoted to the Titanic, the doomed ocean liner built in Belfast and launched in 1911 before it sank on its maiden voyage after striking an iceberg in 1912.