Rebels penetrated the capital of Chad on Saturday, clashing with government troops and moving toward the presidential palace after a three-day advance through the central African nation, a French military spokesman and witnesses said. Col. Thierry Burkhard said groups of rebels gathered outside the capital overnight before about 1,000-1,500 fighters entered the capital, N'Djamena, early Saturday and spread through the city. The French and American governments told their citizens to assemble in secure locations as witnesses reported looting and gunfire near government buildings. Chad, a French colony until 1960, has been convulsed by civil wars and invasions since independence, and the recent discovery of oil has only increased the intensity of the struggle for power in the largely desert country. The most recent series of rebellions began in 2005 in the country's east, occurring at the same time as the conflict in neighboring Sudan's western region of Darfur saw a rise in violence. One Chadian rebel group launched a failed assault on N'Djamena, in April 2006. U.N. officials estimate that around 3 million people have been uprooted by conflicts in the region, including the fighting in western Sudan's Darfur region, which borders Chad, and rebellions in Central African Republic.