NAIROBI, Kenya — Several people were killed on Friday in clashes between the Kenyan police and supporters of the opposition politician Raila Odinga after a disputed contest in which President Uhuru Kenyatta was re-elected, despite reports of voting irregularities.

The police fired water cannons and tear gas as Mr. Odinga’s convoy made its way to Upper Hill in central Nairobi where he addressed supporters. The unrest was broadcast on live television. The police denied that they had fired their weapons or killed anyone, despite several reports by witnesses and journalists to the contrary.