KISUMU, Kenya — The Kenyan opposition leader, Raila Odinga, threw early results of the country’s presidential election into doubt on Wednesday, claiming that the electoral commission’s servers had been hacked to award the incumbent, Uhuru Kenyatta, a significant lead.

Given Kenya’s history of postelection violence, Mr. Odinga’s comments renewed fears of deadly unrest, although he asked supporters to remain calm. Rights organizations have also warned of discrepancies in the preliminary results.