The terrorist attack on Lhubirira secondary school in the city of Mpondwe has claimed the lives of 41 people, including 17 pupils who died in the bomb blast, the local broadcaster reported.
The report added that two local residents died as a result of the terrorist act.
Interpol has condemned the deadly terrorist attack in Uganda and expressed its willingness to provide the necessary assistance in the investigation of the incident, Secretary General Jurgen Stock said.
"I strongly condemn the terrible attack on the school in #Uganda. My thoughts are with the family and friends of the victims. We remain united in the fight against terrorism, and will provide any support requested," Stock tweeted.
Earlier in the day, Ugandan police said the attack had killed at least 25 people and injured eight, who were hospitalized in critical condition. Uganda's armed forces and police continue to pursue the attackers, police said.
Founded in 1995, the ADF operates in both the Democratic Republic of Congo and Uganda, where it is listed as a terrorist organization. The United Nations accuses the ADF of killing hundreds of civilians since 2014. The ADF has close ties to other jihadist groups.