But organizations that fight corruption argue that those investors are exposing in court the corrupt networks of government officials, providing a much-needed check on mineral-rich states. Beyond that, anticorruption campaigners, like the groups Global Witness and the Publish What You Pay Coalition, contend that when nations win debt relief without becoming more accountable, they will simply repeat old mistakes and end up deep in debt once again.

“If it were not for these vulture funds, we would not know any facts about the way our country’s wealth is being taken away,” said Brice Mackosso, a campaigner for greater transparency in the Congo Republic’s government. “We don’t agree with their ultimate aims, but they are the only ones capable of exposing the truth.”

Critics argue that virtually all countries use their debt relief savings to help the poor, and that so-called vulture funds achieve outsize returns from long-forgotten debts at the expense of the world’s poorest people.

Cutting Both Ways

While investor lawsuits may expose nefarious dealings, they may also make governments more secretive to avoid asset seizures. “It can cut both ways,” said Mark Thomas, a senior economist at the World Bank. “It can be a cause of revealing nontransparent practices, but it can also be a cause of those nontransparent practices in the first place.”

Debts are bought and sold all the time, and Western courts have awarded hundreds of millions of dollars in judgments to debt investors. Peru is the best-known example: In 2000, Elliott Associates, whose founder, Paul E. Singer, is a top Republican donor and a backer of Rudolph W. Giuliani’s presidential campaign, won a $58 million judgment on debt it had bought in 1996 for $20 million.

Now African countries are in the sights of debt investors. In 1979, Zambia borrowed $15 million from Romania to buy agricultural equipment. Twenty years later, the two governments agreed to settle the old debt for about $3 million. But a hedge fund, Donegal International, bought it first and sued for about $55 million. This year, a British court ruled that Zambia must pay Donegal $15 million.

The plight of Zambia, a poor country stricken by AIDS, raised awareness of so-called vulture investing in Africa, and debt relief campaigners, celebrities and some members of the Bush administration have taken up the issue.