At least 44 people are confirmed dead after a ferry believed to be carrying up to 500 passengers capsized on the largest lake in Africa.

The boat which was reportedly built for only 300 people sank on Lake Victoria in Tanzania on Thursday afternoon, according to local media.

Mwanza regional commissioner John Mongella said emergency teams safely recovered 37 people with the help of local fisherman who joined the rescue operation.

Local reports say the boat was overloaded with people. However Mr Mongella refused to speculate how many people had been on board, saying “right now our focus is on rescue”.

Such passenger ferries often carry hundreds of people and are overcrowded.

The Tanzania Electrical, Mechanical and Electronics Services Agency, in charge of servicing the vessels, urged patience as rescue efforts began.

The ferry had been travelling between the islands of Ukara and Bugolora and capsized near the area of Mwanza, the agency said.

Accidents are often reported on the large freshwater lake, which is surrounded by Tanzania, Kenya and Uganda.

Some of the deadliest have occurred in Tanzania, where passenger boats are often said to be old and in poor condition.

In 1996 more than 800 people were killed when passenger and cargo ferry MV Bukoba sank on Lake Victoria.

And in 2011 nearly 200 people were killed when the MV Spice Islander I sank off Tanzania’s Indian Ocean coast near Zanzibar.

-with AAP