LUSAKA (Reuters) - Zambia officially charged former President Rupiah Banda for abuse of authority over a Nigerian oil deal, a government spokeswoman said on Monday. Banda, who has been accused of misappropriating more than $11 million during his three years in office, was arrested and then later released on a bond, said Namukolo Kasumpa, a spokeswoman for the government’s investigation team. He will appear in court again on Tuesday, she said. Zambia this month stripped Banda of immunity from prosecution, a sign it was getting closer to bringing formal charges against him. Banda, who led Africa’s top copper producer from 2008 to 2011, has maintained his innocence.