Locals in Nguu/Masumba in Makueni County headed to polling stations on Thursday to vote for their new ward representative.
The seat fell vacant following the death of MCA Harrison Ngui.
Ngui perished in a road crash on the Mombasa-Nairobi highway in June.
All the 34 polling stations across the ward opened their doors shortly after 6 am and recorded long queues in the morning hours.
There are 11,243 registered voters in the ward, according to the Independent Electoral and Boundaries Commission returning officer Moreen Oyaro.
The stakes are high at the by-election which is hotly contested by Daniel Musau of United Democratic Alliance (UDA), Eshio Mwaiwa of Wiper Party, and Timothy Maneno, an independent candidate who is backed by Makueni Governor Kivutha Kibwana and Machakos chief of staff Mwengi Mutuse.
At the local level, the by-election is billed as a petri dish for the supremacy of Mr Mutuse and businessman James Mbaluka who is coordinating Mr Musau’s campaign. The two have declared interest in the Kibwezi West parliamentary seat in next year's polls. The mini-poll is also seen as a contest between Wiper leader Kalonzo Musyoka, Prof Kibwana and Deputy President William Ruto who are separately angling for the presidency.
“Those challenging the Wiper candidate in the upcoming Nguu/Masumba Ward by-election are determined to dim his political star at the national level,” Amani National Congress party leader Musalia Mudavadi said when he accompanied Mr Musyoka and the One Kenya Alliance fratenity to campaign for Mr Mwaiwa. Analysts link the high stakes for the cases of insecurity witnessed on the eve of the by-election.
Goons allied to various political camps clashed on Wednesday night, hours after Makueni County Commissioner Mohammed Maalim directed chiefs, their assistants and Nyumba Kumi cells to quell suspected cases of voter bribery. Businessman James Mbaluka, a key supporter of Mr Musau, fired in the air to scare a team of goons who were baying for his blood. They vandalised his luxury vehicle.
The goons who traversed the ward in luxury cars also attacked a Mutongoi TV crew. Machakos Town MP Victor Munyaka is among those who responded to the incidents which were reported at Kikuumini Police Station. He strongly condemned the violence which he blamed on local Wiper operatives.
Makueni County Police Commander Joseph Napeiyan launched investigations into the incidents.