At least 40 people have died after a ferry carrying hundreds of people capsized on Lake Victoria, Tanzania.

One official told the Reuters news agency the number who drowned could be more than 200. Rescue efforts have been halted until dawn on Friday.

The MV Nyerere ferry overturned near the shore between the islands of Ukora and Bugolora.

It is thought the overloaded vessel toppled over when crowds on board moved to one side as it docked.

Officials have said the ferry was carrying more than 400 passengers. About 100 people were rescued while 32 are said to be in a critical condition.

Exact figures, though, are yet to be confirmed - Reuters said the person who dispensed tickets for the journey also died, with the machine recording the data lost.

"We pray to God to give us hope in such an accident," Regional Commissioner Adam Malima told reporters.

"We pray to God to give us hope that there has not been a high death toll."

Locals joined with emergency teams in rescue efforts on Thursday afternoon.

Accidents are common on Africa's largest lake, Victoria, where boats often depart overcrowded.

More than 800 people died in 1996 when the MV Bukoba capsized. It was one of the worst nautical disasters of the last century. (BBC)