Nigeria's former oil minister Diezani Alison-Madueke has been charged with bribery offences in the UK.

She is suspected of accepting financial rewards for awarding multi-million dollar oil and gas contracts.

A key figure in ex-President Goodluck Jonathan's administration, she also served as the first female president of the oil exporters group Opec.

The 63-year-old, who has been on bail since her arrest in London in 2015, has denied corruption allegations.

Assets worth millions of pounds relating to the alleged offences have been frozen as part of an ongoing probe by the UK's National Crime Agency (NCA).

"These charges are a milestone in what has been a thorough and complex international investigation," Andy Kelly, from the NCA's International Corruption Unit, said.

The NCA says Ms Alison-Madueke, who served as oil minister from 2010 until 2015, is alleged to have benefited from:

• At least £100,000 ($127,000) in cash
• Chauffeur-driven cars
• Flights on private jets
• Luxury family holidays
• Use of multiple London properties
• Furniture, renovation work and staff for the properties
• Payment of private school fees
• Gifts from designer shops such as Cartier jewellery and Louis Vuitton goods.

The US Department of Justice has been able to recover assets totalling $53.1m linked to Ms Alison-Madueke's alleged corruption thanks to evidence provided by the NCA in March, the agency says.

The NCA added that its agents had also worked closely with Nigeria's anti-corruption agency, the Economic and Financial Crimes Commission (EFCC).

Last year, the EFCC said about $153m and more than 80 properties had been recovered from the politician, who was in the cabinet from 2007.

She first held the post of transport minister, then moved to the ministry of mines before taking over the oil portfolio.

Ms Alison-Madueke, who currently lives in London's St John's Wood suburb, will appear at Westminster Magistrates Court on 2 October, the NCA says.

Nigeria is one of the world's largest oil producers, but few of its more than 225 million inhabitants have benefited from this wealth.

It is one of the 13 members of the Organisation of Petroleum Exporting Countries (Opec), set up to deal with the worldwide supply of oil and its price.