The opposition leader went to court disputing the 2013 election results claiming fraud.
Kenyan police have used tear gas and water cannon against stone-throwing protesters during a demonstration in the centre of Nairobi against an electoral oversight body, which the opposition wants to scrap.
Officers on Monday, armed with batons, confronted hundreds of protesters outside the Independent Electoral and Boundaries Commission (IEBC), the third such clash in less than a month. The opposition leader promised more protests.
Kenya does not hold its next presidential and parliamentary polls until August 2017, but politicians are already trying to galvanise their supporters.
The opposition CORD coalition, led by Raila Odinga who lost the 2013 vote, has accused the IEBC of bias.
“For free and fair election, IEBC must go,” read a banner held aloft by one demonstrator.