Tshisekedi, 55, returned to the microphone after 12 minutes, saying: “A famous president of our country said in his time: ‘understand my emotion’.”
He was quoting the late dictator Mobutu Sese Seko, who said those words in 1990 as he was announcing the end of single-party rule in the vast central African country.
“The campaign we had to run… got the better of me,” Tshisekedi added, apologising for the interruption as his predecessor Joseph Kabila looked on impassively through his trademark dark glasses.
State television had interrupted its live broadcast of the historic event after Tshisekedi said, “I don’t feel well”, and sat down as family members came to his side.
During the ceremony, Tshisekedi received the national flag and a copy of the constitution from Kabila, who is stepping aside after 18 years at the helm of sub-Saharan Africa’s biggest country.
Thousands of Tshisekedi supporters, many of them dressed in white, celebrated the historic event outside the Palace of the Nation, the seat of the presidency, in Kinshasa.