United States Secretary of State Hillary Clinton and Angolan Foreign Minister Assuncao dos Anjos address a press conference in Luanda, August 9, 2009. [Agencies]

LAGOS: Nigeria and Angola are Africa's top two oil producers, yet most of their people live in wretched poverty, often in shanties dwarfed by fire-belching derricks.

Corruption has long kept oil revenues from making life better for ordinary people in the two countries, and the growing anger, which swells the ranks of militant groups, creates instability that threatens the world's fuel supply. This week it is drawing the attention of US Secretary of State Hillary Rodham Clinton as she travels across the continent.

World Bank Group President Robert B. Zoellick will also visit Africa this week, a three-nation tour to encourage investor and donor support to help the worlds poorest continent cope with the global economic crisis.

"Some of the biggest gains in fighting poverty in Africa can be made if investors and donors boost support for agriculture, helping Africa achieve food security, while improving rural incomes and facilitating harvest marketing, conservation and agricultural processing," Zoellick said.

Clinton's visits to Angola and Nigeria underscore the increasing importance the US attaches to African oil as it seeks to reduce its need for Mideast oil.

Clinton stressed the need for greater accountability and transparency, and urged the government of President Jose Eduardo dos Santos, in power in the former Portuguese colony since 1979, to adopt a new constitution, investigate and prosecute human rights abuses, and hold promised presidential elections.

Dos Santos "was very positive in his reaction to the points we were making," she told reporters traveling with her.

In 2008, the US imported 1.05 million barrels of oil a day from Nigeria - almost as much as it bought from Saudi Arabia, making the West African country its fifth biggest oil source. Angola to the south, was sixth at 468,000 barrels. For the month of June, Angola edged out Nigeria to become Africa's biggest producer. Nigeria's production has been slowed as militants attack its energy infrastructure.