Mauritania has appealed for international help in providing food and medicine to about 3,000 families displaced by floods.
Tintane, a southern town of 10,000 near the border with Mali, was hit by heavy rains running off nearby mountains, affecting more than 2,000 homes, Abderrahmane Ould Hamma Vezzaz, minister of finance and economy, said.
Speaking to diplomats and representatives of international aid organisations late on Saturday, he said: "Several people were injured, others disappeared and the town has been three-quarters destroyed according to accounts from travellers, who say the water also carried off much of the livestock.
Two people have so far been confirmed dead, but Ould Vezzaz could not confirm how many more were still missing.
"I appeal to international solidarity, notably our development partners," he said.
"The situation is under control, but we are facing problems with food, safety, electricity and providing drinking water, since the water supply network was washed away by the violent tide of water."
Qatar's official news agency QNA quoted on Sunday a source at the foreign ministry as saying that Sheikh Hamad bin Khalifa Al Thani, the country's ruler, had ordered relief assistance to be sent to Mauritania urgently.
Seasonal rain
Ould Vezzaz said schools, health facilities, roads and market places were also damaged or destroyed.
He said the authorities were looking for alternative sites to rebuild houses for residents prepared to move from low-lying districts.
Seasonal rains have arrived across large swathes of West Africa in the past few weeks, giving relief to rural farmers who can now plant their crops, but also bringing devastation to some low-lying and densely populated areas.
Mauritania lies at the western edge of the Sahara and is mostly arid for much of the year, except during the seasonal summer rains which can be torrential.