The Nigerian President, Olusegun Obasanjo, has urged oil firms to open up their accounts to scrutiny as part of a new anti-corruption drive.
Shell and BP say they will support Nigeria's anti-corruption drive
"Whatever you receive, you must publish... I would appeal to extractive industries to participate," he said.
Nigeria, a major oil producer, has been ranked the second most corrupt country in the world after Bangladesh.
Mr Obasanjo was speaking at a Berlin meeting of the global corruption watchdog Transparency International.
The BBC's Ray Furlong in Berlin says Shell and BP - both with large operations in Nigeria - have signalled a willingness to declare payments.
In practice, though, many countries prevent this happening.
Mr Obasanjo's anti-corruption pledge could show the way for other African countries, our correspondent says.
"The fight against corruption must be relentless and continuous," Mr Obasanjo told a news conference.
"The forces of corruption are determined."
Nigeria is Africa's largest oil producer, yet most of its petrol is imported - and most Nigerians live on less than $1 a day.
Under an initiative put forward by UK Prime Minister Tony Blair earlier this year, companies must openly declare exactly what they pay in return for the right to extract oil and other mineral wealth.
Mr Obasanjo, who helped to set up Transparency International, threw his weight behind a similar initiative called Publish What You Pay, pioneered by billionaire philanthropist George Soros.
"We are signing on (to the initiative), then we will show what we receive from royalties, from extractive industries tax," he told the BBC.
The Nigerian leader added that countries with extractive industries "must disclose totally what they receive and companies must disclose totally what they pay".
He also appealed for more international help in repatriating funds siphoned off by former Nigerian rulers, especially the late military ruler Sani Abacha, suspected of having taken up to $3bn out of the country.
"If you are going to deal with the issue of corruption worldwide then there must be a concerted effort," he said.