Southern African countries have been hit by the worst floods in years, killing more than 100 people and displacing thousands, as a tropical storm threatened to bring more pain on Saturday.

As Mozambique braced for the arrival of a strengthening tropical storm Izilda, record river levels across the region threatened to exacerbate floods which have already affected hundreds of thousands of people.

Namibia's government declared a state of emergency last week in areas where floods have affected over 350,000 people, 13,000 of whom were displaced, according to numbers released by the United Nations on Friday.

Another 160,000 people have been affected in Angola.

The Zambezi river, along Namibia's northeastern Caprivi Region, rose to 7.82 metres (25 feet) this week, its highest level in 40 years, before slightly dropping, Caprivi Governor Leonard Mwilima said.

"We have large areas submerged by water and access to several villages is cut off," he said.

Namibia's flood coordinator Erastus Negonga said the death toll stood at 112. Nearly 200 schools have closed, while one hospital and 19 clinics remain cut off due to floods.

In Zambia, 21 districts have been affected by flooding and the army has been called in to assist the worst affected region of Shang'ombo, where they are also helping reconstruct a bridge connecting it to the rest of the country.

"The Zambia air force has been engaged to transport food and fuel to the affected districts," said Davies Sampa, permanent secretary in the vice president's office.

In northern Botswana, rain has caused the Okavango, Zambezi and Chobe rivers to swell, leaving 430 people displaced and submerging eight villages.

The Okavango river which originates in the rain-drenched highlands of Angola empties into the desert north of Botswana, forming the Okavango Delta. The villages of Satau and Parakarungu, with a combined population of more than 1,000, could be swept away by the rising rivers within a matter of days, said district official Orapeleng Modimoopelo.

"Water engineers are telling us these are the worst floods here since 1965," he told AFP.

"The last time a similar flood swept past this place those two villages were sunk, so we expect the same thing to happen, looking at the weight and the speed with which the flood is going."

He said the Kazangula, a crossing point between Botswana, Zambia, Namibia and Zimbabwe, has been impassable for two days.

In Mozambique, where about 4,000 people have been cut off by rising waters, emergency officials monitored Izilda, which was gaining strength Friday in the Mozambique Channel and was likely to strike on Saturday.

Last year, heavy rains in Zambia, Zimbabwe and Malawi caused flash flooding in Mozambique that displaced tens of thousands of people and destroyed almost 100,000 hectares of crops.

Mozambique is no stranger to weather-related disasters. In 2000 and 2001 about 700 people were killed in one of the country's worst floods when torrential rains hit the southeastern African country.

Some are blaming climate change for the floods.

"We must seriously consider the present floods and those of a year ago as having to do with climate change," Guido van Langenhove, a Namibian government hydrologist, told AFP.