CARACAS, Venezuela (CNN) -- Outspoken leftist Hugo Chavez claimed victory in his bid for a new term as Venezuela's president Sunday after the bulk of returns showed him leading challenger Manuel Rosales by a wide margin.

With 78 percent of the votes counted, the National Electoral Council reported Chavez leading Rosales by a margin of 61 percent to 38 percent. Rosales, a provincial governor from the country's oil patch, conceded defeat late Sunday but disputed the margin of his loss.

Chavez thanked supporters gathered outside Miraflores Palace for the win. He also thanked his opponents and urged them to join him in continuing his efforts to remake the country in his self-styled socialist revolution. An outspoken opponent of U.S. policies in Latin America, Chavez was
seeking a second full term as leader of oil-rich Venezuela. He was first elected in 1998, re-elected under a new constitution in 2000 and survived a recall attempt by opponents in 2004.