Nigeria’s militant group, the Boko Haram was paid $3.15million, about N500 million before releasing a French family of seven, a Nigerian government report says.
The BBC said the confidential report was seen by Reuters news agency.
The document did not say who paid the money.
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Both France and Cameroon deny paying a ransom while Nigeria has not commented on the issue.
French news network i-tele reported Friday that a ransom of $7 million had been paid, suggesting either Cameroon President Paul Biya or GDF-Suez had paid it.
The French family, including four children, were captured in Cameroon in February and freed last week.
They were handed over to the Cameroon authorities last Thursday.
The Nigerian report also says that Cameroon freed some Boko Haram detainees as part of the deal, according to Reuters.
If confirmed, transfer of such a significant amount of money given to Boko Haram could serve to strengthen the firepower of the group.
Over the past week, violence in northern Nigeria has escalated as suspected members of Boko Haram have targeted the army and police. Reports say more than 200 civilians have died in the violence, that broke out in Gashua, Bama and Baga, where civilian casualties were estimated by the Red Cross at 187.
While the army is unable to prevent such attacks, Nigerian President Goodluck Jonathan has appointed a committee to prepare the ground for offering an amnesty to the militants, our correspondent says.
The French family, who live in Yaounde, where Tanguy Moulin-Fournier worked for the French gas group Suez, had been returning from a holiday in the Waza National Park in northern Cameroon when they were kidnapped by gunmen on motorbikes on 19 February.
Mr Moulin-Fournier, his wife Albane and four children, aged between five and 12, had been joined on their holiday by his brother Cyril.