Kampala - The Ugandan government has declared three days of national mourning after a collision between a passenger bus, tractor and truck left over 20 people dead.

The mourning period was announced in a government statement on Sunday, which also put the number of dead at 22. 

The Ugandan Red Cross said on Saturday that more than 40 people were killed.

The accident occurred on Friday night near Kiryandongo, about 260 kilometres from Kampala, police spokesman Emilian Kayima said on Saturday, adding that children were among the dead.

The bus rammed into a tractor and hit another beer truck, he said.

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Bus accidents are common on Ugandan roads and are blamed on speeding, drunken driving and the poor mechanical condition of the vehicles.