Videos shared by Kenyans.co.ke show that media coverage of the rally was suddenly interrupted.
Moments later, thick smoke filled the air as teargas was released, causing confusion among supporters and forcing many to scatter in different directions.
Footage from the scene also showed Gachagua, Kalonzo, and other opposition leaders being quickly escorted away from the rally venue.
They were reportedly moved through River Road as clouds of teargas smoke spread behind them.
Security officers were seen trying to manage the growing panic among the crowd as businesses and pedestrians in the area were affected by the commotion.
The rally had been organised shortly after the opposition leaders visited police headquarters to raise concerns over alleged cases of police brutality.
The leaders had earlier stated that their visit aimed to demand accountability and seek answers regarding claims of excessive use of force by law enforcement officers in handling political gatherings and public demonstrations.
Following the disruption, opposition leaders strongly criticised the government, accusing it of deliberately interfering with their meeting.
Speaking after the incident, Gachagua claimed that the chaos was not accidental but had been planned to stop them from addressing supporters.
Gachagua directly blamed Kipchumba Murkomen, alleging that he ordered police officers to disrupt the rally.
He argued that such actions threaten democratic freedoms and the right of leaders to address citizens peacefully.
The claims have sparked debate, with opposition supporters demanding investigations into the incident.
However, security agencies have not immediately issued an official explanation regarding the use of teargas at the rally.
Police often maintain that such measures are taken to control crowds and maintain public order, especially in busy business areas where large gatherings can interfere with normal activities.
The incident caused temporary disruption of business and transport activities in parts of the city centre.
Traders were forced to close their shops briefly, while motorists experienced delays as crowds dispersed and security officers attempted to restore order.
