LONDON, Dec 14 (Reuters) - The African Export Import Bank has raised $520 million via a loan led by Japanese bank MUFG towards its credit facility to help African countries overcome the effects of the coronavirus pandemic, MUFG said on Monday. The deal, which tapped Japanese investors, was the first to be covered by Nippon Export and Investment Insurance, the Japanese government trade and investment insurance agency, MUFG said in a statement. Afreximbank announced the launch of a $3 billion Pandemic Trade Impact Mitigation Facility in March to help countries avoid trade payment defaults, support foreign exchange reserves and assist commodities exporters struggling with declining revenues. (Reporting by Tom Arnold; Editing by Susan Fenton)