In-form Tusker picked a 4-1 win over Kaiobangi Sharks during a Football Kenya Federation Premier League tie on Thursday at Kasarani Annex.
Jackson Macharia, Henry Meja, and Luke Namanda scored for Robert Matano's side while Posta Rangers' goal was struck by Ezekiel Okare.
Tusker's first open chance came in the eighth minute but Hillary Wandera's effort went straight into Bryne Omondi's waiting hands. In the 19th minute, Macharia attempted a long-range shot after a quick counter-attack but he missed the target narrowly.
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Jackson Dwang's free-kick from a vantage point which was Posta Rangers' first close chance, went over the bar in the 29th minute.