“So far 20 people have been confirmed dead, and nine (9) rescued,” the Uganda police force said on Twitter, which is being rebranded as X.
The boat was carrying charcoal, fresh food and fish when the accident occurred around 5:00 am (0200 GMT), the police said.
“The cause of (the) accident is attributed to overloading and bad weather,” they added, saying that around 34 people were believed to be onboard.
“We appeal to members of the public who travel on waters to always wear life jackets and not to overload their vessels.”
Africa’s largest lake has witnessed many boat disasters, with the accidents often blamed on overcrowding and poor weather.
Thirty-two people died in November 2018 after a pleasure boat sank on Lake Victoria during bad weather, with Uganda police saying the vessel had more than 90 revellers on board.
In September that year, hundreds died when the MV Nyerere passenger ferry sank on the Tanzanian side of Lake Victoria.
With a surface area of 70,000 square kilometres (27,000 square miles), oval-shaped Lake Victoria is roughly the size of Ireland and is shared by Tanzania, Uganda and Kenya.
It is not uncommon for ferries to capsize on the lake and the number of fatalities is often high due to a shortage of life jackets and the fact that few people know how to swim.
Boats tend to be the only form of transportation in parts of Africa’s Great Lakes region, and are often overcrowded and poorly maintained.
Accidents are also common along Lake Albert, which marks the border between Uganda and the Democratic Republic of Congo.
At least 26 people died in December 2020 when their boat sank on Lake Albert. That accident was blamed on bad weather.