The M23 rebel group has seized large parts of the mineral-rich eastern DR Congo this year.
The UN said the attack on its helicopter "may constitute a war crime".
China said it was keen on helping Africa attain the stability it needs to realize its growth and development goals.
Natasha Akpoti-Uduaghan had accused Senate President Godswill Akpabio of sexual harassment.
Sixteen people were injured, according to local civil society group Plataforma Decide.
He insists that he was raised very well by his late mother and had never harassed any woman.
US President Donald Trump said that "nobody has ever heard of" the African country of Lesotho.
It said the attempts are unhelpful for peace and security for the country.
IGAD says they are alarmed by the recent reports of escalating tensions and armed clashes in Nasir County
