Nigeria's President Muhammadu Buhari has signed into law an oil bill first introduced in parliament nearly 20 years ago.

The Petroleum Industry Act - which amalgamates some 16 previous laws - overhauls nearly every aspect of oil and gas production.

It aims to attract more foreign investment and increase the local production of fossil fuels. It also reduces the government’s vice-like grip on the Nigerian National Petroleum Corporation, the state oil company whose operations are widely seen as opaque.

Companies are now required to invest 3% of their operating expenses into projects for local communities.

The Nigerian energy sector has long been beset by corruption, inefficiency and insecurity.

It is Africa's biggest exporter of oil, yet imports most of its processed fuel.

President Buhari is likely to claim the law as a major achievement of his government.