The panel of judges said the CNL had failed to provide sufficient evidence and ruled the complaints were "null and void", validating Evariste Ndayishimiye's victory with 68.7 percent of the vote.
"We don't have a problem with the WHO, we have a problem with the WHO's representative in Malabo," Prime Minister Pascual Obama Asue said in remarks broadcast on state television.
"It's deplorable that almost 70 years since racial segregation was abolished in America, people of color are still routinely slaughtered for the color of their skin," the ANC said.
"Zimbabwe is not and has never been an adversary of the United States of America," Zimbabwe's Foreign Minister Sibusiso Moyo said.
Maesaiah Thabane is suspected of orchestrating the shooting of Lipolelo Thabane, who was gunned down outside her home in the capital Maseru.
The opposition decried "the will of those in power to deprive Nigeriens... of all privacy in their communications."
In the six months to April 2020, at least 296 people were killed, 151 wounded and 38 raped, including women and children, mostly by fighters linked to the CODECO rebel group, said a report by the United Nations Joint Human Rights Office (UNJHRO).