ABUJA, June 9 -- When a developing country tries to raise money without passing through the West's front door, the West's institutions tend to notice. Nigeria is attempting exactly that, and the International Monetary Fund has stepped forward with a warning. Africa's most populous nation wants to borrow as much as $5 billion through a private deal with a Gulf bank, and the Fund says the arrangement is too opaque to be trusted.

The IMF said on Tuesday that Nigeria's plan to borrow through a total return swap with First Abu Dhabi Bank carried real risks, calling such instruments complex and hard to see into. Christian Ebeke, the Fund's mission chief for Nigeria, put it plainly. "Usually they are opaque so the terms are not always very tran...