Ssenyonyi, who said he was travelling to monitor the electoral process on behalf of the National Unity Platform (NUP) candidate, Irene Nampala, claimed authorities blocked his journey from Bukakata Landing Site in Masaka District to Kalangala.
In a statement posted on his social media platforms, Ssenyonyi said he spent nearly two hours aboard a ferry that was scheduled to transport passengers to Kalangala but failed to depart.
"I've been seated on the ferry meant to go to Kalangala from Bukakata for close to two hours, but it has not set off. I'm told there's been an instruction not to set off because there is no 'clearance' yet for me to proceed to Kalangala, where I'm meant to be one of the supervisors for our candidate Irene Nampala's team in the by-election," Ssenyonyi said.
He further alleged that while he remained stranded at the landing site, he was receiving reports of suspicious vehicle movements and alleged ballot stuffing at some polling stations in the district.
Ssenyonyi also claimed that after he boarded a second ferry, the vessel was ordered to turn back midway through the journey because he was on board.
However, the Greater Masaka Regional Police spokesperson, Twaha Kasirye, said he was unaware of any directive or police operation aimed at preventing Ssenyonyi from travelling to Kalangala.
"I am not aware of any such directive stopping him from travelling," Kasirye said.
The allegations had not been independently verified by the time of publication.
The incident unfolded as voters across Kalangala District participated in the by-election to elect a new Woman Member of Parliament following the death of former legislator Hellen Nakimuli earlier this year.
The Electoral Commission had not immediately commented on Ssenyonyi's allegations regarding the ferry delays or the conduct of the election.