The 56-year-old rocker and the Nigerian commodities billionaire toured the camp, which houses many of the 2.3 million people left homeless following raids by feared African Islamist extremist group Boko Haram.

Bono, real name Paul Hewson, delivered an emotional plea for more funding to be directed towards the refugees, insisting more resources were necessary to guard against malnutrition.

"It's clear that the story of malnutrition is not getting out here," he told the BBC. "There's 50,000 children going to die by the end of the year (16). 50,000 children are going to die if the UN (United Nations) don't get what they are looking for, which is, I think, 300 million (dollars)."

Bono revealed Aliko, who he dubbed the "Bill Gates of Africa", had brought him to the camp to see the hardship suffered by refugees firsthand.

The Vertigo singer admitted he was shocked to see several young girls who had been married off against their will by members of the Islamist extremist group.

"I wasn't really prepared to see a nine-year-old child bride with all her friends who are child brides in such a collection and realise that's actually what Boko Haram looks like," he said.

Since its rise in 2009, Boko Haram has taken over large parts of the north of Nigeria, imposing an extreme form of Sharia law and carrying out a campaign of terror aimed at destabilising the Nigerian government.