Delegates questioned the move, noting that there were no protests to warrant such measures.
Some expressed concern over what they described as unnecessary force, saying the gathering was intended to be peaceful.
Despite the police barricade, tensions rose as more supporters continued to arrive.
A section of those present challenged the officers’ decision to restrict access, insisting they had a right to hold their meeting at the venue.
One of the supporters was heard questioning the police action, saying, “Ati polisi afunge mkutano ya nani? Tumeingia mapema!”
The situation remained fluid as crowds gathered near the entrance, with some attempting to push their way through the police line.
Videos circulating online showed a large number of people making their way towards the venue, chanting and waving as they advanced.
In one clip, voices could be heard declaring, “We have gained entry to Ufungamano kwa LAZIMA. Sisi ndio wanainchi!” as the crowd pressed forward.
It was not immediately clear why police had moved to block access to the venue, as organisers maintained that the event had been planned in advance.
The deployment of anti-riot equipment, including water cannons, suggested authorities were preparing for possible unrest, even as delegates insisted their intentions were peaceful.
The standoff created confusion among attendees, many of whom had travelled from different parts of Nairobi and beyond to participate in the convention.
Some were seen engaging officers in heated exchanges, while others waited nearby, hoping the situation would be resolved.
By mid-morning, the crowd had grown significantly, with supporters continuing to gather outside Ufungamano House.
The atmosphere remained tense but largely controlled, with police maintaining their positions at the entrance.