At least 1,800 people in Tanzania's southern region of Mtwara have been left homeless after their houses were submerged by flash floods caused by the ongoing heavy rains, an official has said.

Ahmed Abbas, the Mtwara regional commissioner, said the flash floods occurred in the past week after the Ruvuma River overflowed following heavy rains upstream.

"The flash floods submerged over 150 houses in Maurunga and Kilambo wards in Mtwara district leaving 528 households with 1,800 people homeless," Abbas said.

The homeless victims have been sheltered in primary schools as the regional authorities were organising relief supplies, including tents and food, for the victims, he said.