The chairperson of the African Union Commission (AUC), Dr Moussa Faki Mahamat, has called for cooperation among nations in combating multiple international challenges.
"We are meeting at a time when there is a worrying weakening of multilateralism, even though its principles seemed to be built on solid foundations. Our summit is held in a context that is lacking, not only because of the acute challenges facing our continent, but also because of the uncertainty that hangs over the international system.
"The situation is such that it makes us say that we are at the crossroads," he said.
"...The multiplication of unilateral measures has the potential to dangerously weaken the capacity of the international community to respond effectively to the complex challenges it faces, the rise of national selfishness, the trivialisation of xenophobia, the rejection of the other," the chairman added.
Complimenting Dr Mahamat, UN Secretary General Antonio Guterres stressed the need for advancing multilateralism.
"The United Nations and the African Union need to closely work with the African Union peacekeepers, fighting illicit financial flows, combating climate change, migration and the fight against corruption," he said.
"Combating corruption, tax evasion and illicit financial flows requires commitment and accountability," Mr Guterres said, commenting on the theme of the summit.
Palestinian President Mahmoud Abbas, who also addressed the African leaders, commended Ethiopia, Egypt and other African countries at the Security Council, which supported the Palestine vote against President Donald Trump's decision to move the US Embassy to Jerusalem.
Zimbabwean President Emmerson Mnangagwa, who replaced Robert Mugabe said: "He (Mugabe) is well, self-secured and it is my duty to preserve his legacy as founding leader of our republic. The transition, as you are aware, was peaceful."
The new President of Liberia George Weah noted that he took seriously the responsibility of becoming a head of state.
"With your help, I would be able to deliver to my people and help them achieve their aspirations. I look forward to working with you in the spirit of solidarity.
"Fighting corruption is a sustainable path for Africa's transformation.
"We can put under control corruption, particularly through institutional transformation," he said.