Lombardi rejected criticism for Mugabe's presence, remarking that it is not the policy of the Holy See to make invitations.
"Those who wish to come are welcome, no one is refused," he said.
Religious leaders covered a broad range, and included 33 Christian churches, 16 Jewish leaders, as well as Muslim, Buddhist and Sikh leaders.
The ecumenical patriarch of Constantinople, Bartholomew I, also participated. It's the first time the spiritual head of Orthodox Christians attend a papal inauguration since the Great Schism between western and eastern Christianity in 1054 .
"This pope is like one of us. We are so tired of a pompous, scandal hit church. Now we have a pope who takes inspiration from St. Francis," Luisa Marchetti, a pilgrim from Sanremo, told Discovery News.
"I am confident he will change things dramatically and for the best.
Let's hope they let him do that," she added.
Although Pope Francis has been winning hearts with his humble, warm and direct style, he is still criticized from leftists at home for failing to speak out during Argentina's dictatorship.