Renewed fighting in DR Congo as regional powers step up ceasefire efforts / Why DR Congo's army struggles against the smaller M23 / Children use guns discarded by DR Congo army, as M23 rebels advance in south of Bukavu / A leader of Congo's rebels vows to fight on / Congolese troops retake control of city of Bukavu -- presidency / Rwanda-backed rebels advance and Congolese forces retreat from eastern Congo's second largest city / The DR Congo rebel leader whose fighters have created turmoil / Crisis in the DRC: In Goma with the victims of the war between the M23 and the Congolese army / Congolese army fights to repel Rwanda-backed rebels in fighting that has killed some 700 people