"These are wounds inflicted by minorities who cling to power and wealth, who selfishly squander while a growing majority is forced to flee to abandoned, filthy and run-down peripheries," the 78-year-old pontiff told crowds in the Nairobi shanty town of Kangemi.
Francis, whose visit to the slum is a highlight of his three-nation Africa tour, condemned the "dreadful injustice of urban exclusion."
Wild singing and ululating broke out as he arrived early today, his popemobile weaving through streets in a sea of tin-roofed homes.
"I realise the difficulties which you experience daily. How can I not denounce the injustices which you suffer?"
Also Read
People arrived long hours before dawn in the hope of catching a glimpse of the pope, who has made efforts for social justice a hallmark of his tenure.
Francis criticised the lack of "infrastructures and basic services", including sewerage, electricity, good roads, school and hospitals.
"This situation of indifference and hostility experienced by poor neighbourhoods is aggravated when violence spreads and criminal organisations, serving economic or political interests, use children and young people as 'cannon fodder' for their ruthless business affairs," he added, singling out the role women play in binding such societies together.
"I also appreciate the struggles of those women who fight heroically to protect their sons and daughters from these dangers.