government groups in the United States continued to rise last year, fueled by racial tensions, conspiracy theories and anger over economic inequality, according to a report by the Southern Poverty Law Center. The most explosive growth came from the so-called Patriot movement, whose adherents view the federal government as their enemy. The Patriot movement reached a peak in 1996, a year after right-wing extremist Timothy McVeigh set off a truck bomb outside the Oklahoma City federal building, killing 168 people. McVeigh and a co-conspirator were convicted, and McVeigh was executed. The number of Patriot groups, a largely rural phenomenon sometimes referred to as the militia movement, increased to 1,274 groups in 2011 from 824 in 2010, the report released on Thursday said. The number of those organizations has swelled in recent years since the US economy slumped into recession and Democratic President Barack Obama was elected in 2008, said the law center, which has tracked extremist groups for three decades. A backlash against federal bail outs of the bank and auto industries, and discredited allegations that Obama was not born in the United States and therefore disqualified to be president, provided believers with the rationale to join such groups, according to the report. Heated political rhetoric from this year's presidential campaign could attract more adherents, said Mark Potok, senior fellow at the center and editor of the report.