By Chris Mfula and Stella Mapenzauswa LUSAKA (Reuters) - President Edgar Lungu was ahead of his main rival on Saturday in early counting from Zambia's presidential election, but the main opposition said its count showed their candidate ahead and the vote may have been rigged. Lungu faces a stiff challenge from United Party for National Development (UPND) leader Hakainde Hichilema, who accuses him of failing to steer the economy out of its slump after Africa's second-largest copper producer was hit by weak commodity prices.
