Ban Ki-Moon continues: "Mandela showed us the way with a heart larger than this stadium and an infectious smile".
"His long walk [is] complete," he adds.
UN Secretary General Ban Ki-Moon says that tens of thousands of people are gathered in "celebration of a mighty life".
He adds: "I hope we will be able to see the rainbow soon through the rain of sadness.
"South Africa has lost a hero. We have lost a father."
UN Secretary General Ban Ki-Moon has said that Syria's president Bashar al-Assad "has committed many crimes against humanity".
He added that he expects a report by UN weapons inspectors to confirm that chemical weapons were used in Syria.
The Secretary-General has accused the Security Council of suffering from an "embarrassing paralysis" on Syria and called on the international community to overcome the deadlock.
Ban Ki-Moon says he is considering asking the UN Security Council to demand Syria immediately transfer chemical weapons to safe sites where they can be destroyed.
UN Secretary-General Ban Ki-moon has appeared to question the legality of US plans for military action in Syria saying that the use of force is only legal in self-defence or with Security Council backing.
He also added that if the UN inspectors confirm the use of chemical weapons in Syria, the Security Council should overcome its differences and take action.
"If confirmed, any use of chemical weapons by anyone under any circumstances will be a serious violation of international law and outrageous war crime," he told reporters. "Any perpetrators must be brought to justice. There should be no impunity."
Ban Ki-moon has said that an attack by the US to punish alleged Syria chemical weapons use could unleash more turmoil in the region.
Samples taken by UN weapons inspectors from the site of an alleged chemical attack in Syria have been sent to laboratories for testing and will arrive "within hours," a UN spokesperson has said.
Since the return of the Mission last Saturday, the UN team worked around the clock to finalise the preparations of the samples in view of their shipment to the designated laboratories.
The samples were shipped this afternoon from The Hague and will reach their destination within hours.
The designated laboratories are prepared to begin the analyses immediately after receipt of samples.
Secretary General Ban Ki-Moon has held talks with the chief inspector, Dr. Ake Sellström, about how the tests can be sped up and will brief members of the Security Council on Tuesday.
The UN Secretary General Ban Ki-moon returned to New York on Thursday evening and intends to engage with member states on developments in Syria, a spokesperson said.
His first meeting is due take place with the permanent members of the Security Council.
United Nations Secretary-General Ban Ki-moon said the chemical weapons team sent to Damascus to investigate alleged chemical attacks will leave Syria by Saturday morning.
He added that the experts would continue their investigations until Friday.
UN inspectors need four days in Syria to conclude their investigation into last week's alleged chemical attack and analyse their findings, UN Secretary-General Ban Ki-moon has said.
"They are working very hard, under very, very dangerous circumstances," Ban said. "Let them conclude their work for four days, and then we will have to analyse scientifically with experts and then I think we will have to report to the Security Council for any actions."