WASHINGTON (Reuters) - The U.S. Justice Department on Thursday sued two towns on the Utah-Arizona border that are dominated by a polygamist Mormon sect, citing religious discrimination and civil rights violations against residents who do not share the majority faith.The lawsuit against the twin cities of Colorado City, Arizona, and Hildale, Utah, said the towns and their joint police department and utility providers had allowed the sect to unduly influence the provision of public services, including policing.Most of the residents of the towns are members of the Fundamentalist Church of Jesus Christ of Latter-day Saints, a breakaway Mormon sect whose leader, Warren Jeffs, is serving a sentence of life plus 20 years in prison in Texas for raping two underage girls he wed in "spiritual marriages.""City governments and their police departments may not favor one religious group over another and may not discriminate against individuals because of their religious affiliation," Thomas E. Perez, Assistant Attorney General for the Justice Department's Civil Rights Division, said in a statement announcing the suit.The complaint said the towns' joint police force failed to investigate crimes against non-FLDS members or refused to arrest FLDS individuals who had committed crimes against those who were not in the church, such as destroying crops on a farm of a non-FLDS member and trespassing on property occupied by non-FLDS members.The lawsuit also accused the cities of refusing to issue building permits to prevent individuals from constructing or occupying existing housing based on their religious affiliation.The behavior is in violation of the First, Fourth and Fourteenth Amendments to the U.S. Constitution and the Fair Housing Act, the Justice Department said.The polygamist FLDS sect, which experts estimate has 10,000 followers in North America, has been condemned by the mainstream Mormon Church and is accused of promoting marriages between older men and girls.(Reporting By Lily Kuo; Writing by Cynthia Johnston; Editing by Paul Simao and Eric Walsh)