SAKE/GOMA - Congolese troops were fighting back on Thursday against rebels who rejected calls from African leaders to quit the eastern city of Goma, captured earlier this week. Thousands of people fled the area of clashes around the town of Sake, as M23 rebel fighters rushed from Goma to reinforce their positions there against a counter-offensive by the army. The rebel movement, widely believed to be backed by Rwanda, has vowed to "liberate" all of the vast, resource-rich country after taking Goma, a provincial capital on the Rwandan border, ramping up tensions in a fragile region. The head of M23's political arm said the rebels would not retreat despite the call to do so from governments in central Africa, preferring to hold their ground until President Joseph Kabila opens direct talks with them: "We'll stay in Goma waiting for negotiations," Jean-Marie Runiga told Reuters in the city. "They're going to attack us and we're going to defend ourselves and keep on advancing." Rebel fighters seized the sprawling lakeside city of a million people on Tuesday after government soldiers retreated and U.N. peacekeepers gave up trying to defend it. The next day the rebels moved in unopposed to Sake, a strategic town about 25 km (15 miles) west along the main road. It was there that government troops and allied militia were hitting back in fighting the flared up late on Wednesday. Regional and international leaders have been scrambling to halt the fresh conflagration in the Great Lakes, a region of many colonial-era frontiers and long a tinderbox of ethnic and political conflict, fuelled by mineral deposits. On Wednesday, foreign ministers from the states of the Great Lakes region demanded the rebels leave Goma and halt their advance, and Kabila - in a concession to the rebels that fell short of opening talks - promised to look into their grievances. "I'm not confident, because I've already waited for three months in Kampala for talks," Runiga said of a recent spell in the capital of Uganda, which has tried to mediate in the Democratic Republic of Congo (DRC). Neighboring Uganda and Rwanda had no right to make demands of M23, added the group's political chief, who styles himself Bishop Runiga, a post he holds in several Congolese churches.