Civil servants and other public officials in Nigeria routinely receive bribes totalling 400 bn Naira ($1.27bn; £985m) per year, according to a government survey.

The Nigerian Corruption Survey 2017, conducted by the National Bureau for Statistics (NBS), revealed that almost a third (32 out of 100) of Nigerian citizens who had contact with a public official between June 2015 and May 2016 bribed them.

The survey – supported by the UN and the European Union – is based on 33,067 interviews with adults across the country.

It estimated that 82.3 million bribes were paid in Nigeria in the time window considered. The majority of them were paid in cash to police officers (the most common target to receive bribes), prosecutors and judges.

"Almost 70% of bribes are paid before a service is rendered," said the report.

"With such a large portion of public officials initiating bribery episodes it seems that many public officials show little hesitation in asking for a kickback to carry out their duty and that bribery is an established part of the administrative procedure in Nigeria."

In addition to cash, other forms of bribe payments take place in the country, including provision of food and drinks, as well as also sexual services.

The survey further said that Nigerians considered bribery as the third most important problem in their country, following unemployment and rising costs of living.

Nigeria, one of Africa's biggest oil producers, is facing an economic crisis exacerbated by a drop in oil production due to renewed violence at the hands of militant groups in the Niger Delta region.

Nigeria's President Muhammadu Buhari – currently on media leave in the UK – vowed he would eradicate corruption when he took office in 2015. The leader has sought the help of several countries, including the UK, the US and the United Arab Emirates (UAE), to locate and repatriate embezzled Nigerian funds reinvested outside the African nation.

Last year, the head of state defended a raid targeting several judges suspected of corruption. The country's security agency said it had seized $800,000 in cash during raids at the houses of three judges at the weekend in october 2016.

The move was slammed by the Nigerian Bar Association (NBA) as a "gestapo-like" operation.

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Police stand watch over protesters in Nigeria\'s capital, Abuja
Police officers were the largest group of bribe takers between June 2015 and May 2016 Reuters