UPDATE 12.45: Catholic leaders on Saturday appealed for calm and asked security forces to exercise caution during protests.
"We appeal to them to restrain themselves from using excessive force in handling crowds," said John Oballa Owaa, vice chairman of the Kenya Conference of Catholic Bishops. "No life should be lost because of an election."
The bishop said any dispute over the election should be resolved peacefully and by "legal norms as provided in the constitution."
Earlier: Kenyan police have shot and killed two people during riots by opposition supporters after President Uhuru Kenyatta was declared the winner in national elections.
Leonard Katana, a regional police commander, said the deaths occurred on the outskirts of Kisumu, a city where opposition leader Raila Odinga has strong support.
Mr Katana said another five people were injured by gunfire in Kisumu.
Also on Saturday, Kenyan police opened fire to disperse opposition protesters who blocked roads and set up burning barricades in a slum in Nairobi, the capital. An Associated Press photographer saw police firing live rounds in the Mathare area.
Mr Kenyatta on Friday appealed for unity after the Kenyan election commission announced results following several days of vote-counting. Mr Odinga has alleged that the election was rigged.