Former president Mary Robinson will lead a panel to investigate the leader of the African Development Bank (AfDB), accused by whistleblowers of corruption, the bank said.

Akinwumi Adesina, 60, became the first Nigerian to helm the AfDB in 2015 - but a 15-page report earlier this year claimed that under his watch the bank had been tarred by poor governance, impunity, personal enrichment and favouritism.

He was cleared by the organisation's ethics committee, but international pressure has mounted with the United States calling in May for an independent investigation.

Mrs Robinson will lead the probe, alongside Gambia's Chief Justice Hassan Jallow and the World Bank's integrity vice president Leonard McCarthy, the bank's board of governors said.

The governors of the AfDB, one of the world's five largest multilateral development lenders, expressed "their complete confidence" in the panel.

The inquiry is due to deliver its findings in two to four weeks.

The AfDB plays an important if largely behind-the-scenes role in African economies, financing projects in agriculture, health, energy, education, transport and other development sectors.