Cholera has overwhelmed the healthcare system and sparked calls for international assistance for the tiny Portuguese colony in West Africa, worst hit in the current outbreak, where cholera is a constant menace during annual rains.

The United Nations says that six other countries -- Benin, Burkina Faso, Mali, Mauritania, Niger and Togo -- need urgent aid and the floods are increasing the risk of deadly diseases.

About 150,000 have been forced out of their homes and 300 infected by cholera in Benin alone. Over 10,000 people fled high waters in Togo, where bridges were washed away in July, pushing up the price of food.

This year's crisis follows the displacement of hundreds of thousands of people last year. But the impact has been exacerbated as one of the world's poorest regions is already grappling with the high food and fuel prices.

"It's looking bad all over the place as there is only the Bijagos Archipelago that has not been affected," said Guinea-Bissau Minister of Health Camilo Simoes.

As a result, the government has called for help from abroad and issued a decree banning the sale of vegetables, doughnuts and sachets of water at home, he said.

Cholera is mainly transmitted through contaminated water being drunk or used in food preparation. It begins with acute watery diarrhoea and can kill by dehydration and kidney failure within hours.

Staff at the Simao Mendes hospital in the capital of Bissau were overwhelmed on Thursday, treating patients lying on the floor in corridors as they had run out of beds.

On Monday and Tuesday alone, 170 new cases were registered across the country, UN Children's Fund UNICEF said.

Tents promised by the United Nations to shelter cholera patients have not yet arrived, said doctors who are dealing with a dozen new patients arriving at the hospital every day.

"The situation is beyond our control," said Agostinho Semedo, director of the Simao Mendes hospital.

"People must respect the laws that have been put in place. The population must take part in the fight by putting an end to funerals where animals are sacrificed," he added.

The health crisis has hit Guinea-Bissau amidst a political instability that has seen the government replaced, parliament dissolved and a coup attempt.

Parliamentary elections are scheduled for November but state authority has been further weakened by drug dealers using the country as a hub for the cocaine trade to Europe.