Upon independence in 1960, the former French region of Middle Congo became the Republic of the Congo. A quarter century of experimentation with Marxism was abandoned in 1990 and a democratically elected government took office in 1992. A two-year civil war that ended in 1999 restored former Marxist President Denis SASSOU-Nguesso, who had ruled from 1979 to 1992, and sparked a short period of ethnic and political unrest that was resolved by a peace agreement in late 1999. A new constitution adopted three years later provided for a multi-party system and a seven-year presidential term, and elections arranged shortly thereafter installed SASSOU-Nguesso. Following a year of renewed fighting, President SASSOU-Nguesso and southern-based rebel groups agreed to a final peace accord in March 2003. SASSOU-Nguesso was reeelected in 2009 and, after passing a referendum allowing him to run for a third term, was reelected again in 2016. The Republic of Congo is one of Africa's largest petroleum producers, but with declining production it will need new offshore oil finds to sustain its oil earnings over the long term.