• Earlier, skirmishes was experienced at Kibra Mashimoni after an incident of voter bribery.
Two people have been arrested for allegedly bribing voters at two polling stations in Kibra.
The two, a man and a woman, were arrested separately on Thursday at YMCA polling station and Old Kibra Primary school.
The two were roughed up and put in a police car amid tight security in the polling stations.
Nairobi Area police boss Philip Ndolo said they will be charged after witnesses come out to testify against them.
"We will only take them to court when there is evidence," he told the Star as the residents were seen baying for their blood.
"The incident here was of a person who appeared to be moving from line to line. Voters identified him and rescued him," Rarieda MP Atiende Amollo said.
Earlier, skirmishes was experienced at Kibra Mashimoni after an incident of voter bribery.
Residents asked why some people were being given money.
"Kama mnajua mko na kura mbona mnagawa pesa. They are giving people Sh200 each. We don't want your money," One was heard shouting.
Voters troop to the polls in a contest considered a dress rehearsal for the 2022 General Election and a test of muscle for both DP William Ruto and ODM party leader Raila Odinga.
The winner succeeds Okoth who died in July, triggering the hotly contested by-election.
ODM's Bernard Okoth, Ken's brother, faces Jubilee's McDonald Mariga, an ex-football star and Eliud Owalo of ANC. Twenty-four candidates are on the ballot.
The poll is being overseen by 188 presiding officers and 625 clerks. There are 118,658 voters listed on the IEBC roll.