The incident caused major disruption along one of Nairobi's busiest transport corridors as frightened drivers searched for safer routes to escape the chaos.
Witnesses at the scene claimed some of the youths were armed with machetes, clubs and other crude weapons.
Several motorists alleged they were robbed of valuables after the group surrounded vehicles trapped in the heavy traffic, while others reported that stones were hurled at moving cars, damaging windscreens and forcing drivers to abandon their normal routes.
Some people were seen running for safety while others cautiously moved between stationary vehicles amid fears that the situation could deteriorate further.
The motive behind the road blockade had not been officially established by the time of reporting.
However, some witnesses alleged they heard members of the group repeatedly shouting "Sisi Tumetumwa," a phrase that quickly attracted widespread attention on social media as Kenyans questioned who they claimed had sent them.
Hundreds of commuters were affected as the disruption slowed movement between Nairobi's central business district and neighbouring areas, including routes leading towards Kiambu County.
Many motorists remained inside their vehicles while others turned back or diverted through alternative roads to avoid the confrontation.
By the time the incident unfolded, the National Police Service had not issued an official statement confirming arrests, injuries or the extent of property lost during the robbery claims. Emergency response efforts were also yet to be publicly communicated.
The latest incident has renewed public concern over the growing trend of criminal elements infiltrating public gatherings and targeting innocent road users.
Many Kenyans have since called for stronger security measures along major highways to protect commuters and ensure those responsible are identified and brought to justice.
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