A teargas canister was on Friday lobbed at a roadside rally addressed by Opposition leader Raila Odinga in Kiambu.
The canister was thrown from among the crowds as residents listened to speeches from Azimio leaders who accompanied Raila.
After the canister exploded, next to the motorcade, Wiper leader Kalonzo Musyoka who was on the microphone said the act was uncalled for.
"The officer in charge of that should have his name already at the International Criminal Court at the Hague," Kalonzo said.
It was not clear whether the canister was lobbed by a police officer, but citizens are not allowed to be in possession of such security gear.
Kalonzo claimed that the canister belonged to the police and asked the Inspector General of police Japhet Koome to take action.
Leaders were forced to retreat into their vehicles before emerging after normalcy returned.
However, the rally went on smoothly after the temporary disruption in Kiambu.
President Ruto meets Ambassador Mo Farah at State House