Sudanese authorities have said forecasts show the level of the Blue Nile River will continue to rise and the situation remains critical in many of the country's states after weeks of torrential rains and flooding that have left more than 70 people dead.

The level of the river, which runs through eastern and southeastern Sudan, has been rising steadily over the past weeks, forcing hundreds of families living along its path to abandon their homes.

Blue Nile State has ordered the closure of all schools as a precautionary measure and the International Organization for Migration and Sudanese officials have announced the suspension of returning internally displaced persons (IDPs) by barge to southern Sudan.

"We expect more floods because of continuing heavy rains on the Ethiopian plateau," Awad Widatallah Hussein, spokesman for the government's emergency response committee, told IRIN on 7 August.

The rains from the Ethiopian plateau feed the Blue Nile and the River Gash, which has already burst its banks, submerging nearby villages, sweeping away roads and isolating towns.

More than a dozen of Sudan's 26 states have been affected by the floods, including those in the south.

We expect more floods because of continuing heavy rains on the Ethiopian plateau

"We now have 71 people dead," said Hussein.

The situation, he added, remained critical in certain states, with more areas likely to be affected as water levels continue to increase.

In Khartoum, the worst affected state in the country, officials have been using aircraft to spray the city with insecticides. Health officials warned that pockets of stagnant water could breed mosquitoes and increase the potential for diseases.

However, government officials said no serious outbreak had been reported in connection with the floods.

"Although the floods came earlier than expected, the response has been swift and successful," David Gressly, acting United Nations Resident and Humanitarian Coordinator in the country, said in a statement.

"We had contingency measures in place and were able to prevent further distress to the population," he added.

According to the UN, the floods have destroyed at least 30,000 houses, directly affecting more than 365,000 people. "If current flooding patterns continue unabated, the situation will deteriorate considerably," Gressly said.

The UN and its partners, with support from the government, have so far helped up to half a million people. This included the provision of purification products and hygiene education.

In Kassala, near the Eritrean border, tankers have been delivering clean water to the most affected neighbourhoods, covering at least 10,000 people.

"Over the rest of the rainy season, clean water - potentially life-saving - will continue to be a priority need for hundreds of thousands," the UN said.

Despite the preventive measures put in place, the UN added, some 637 cases of suspected acute watery diaorrhea were reported in the eastern states of Gedaref and Kassala, resulting in 39 deaths.

"We are working closely with the government to reach accurate estimates of the needs of those affected and the funding requirements," said John Clarke, a UN official coordinating the response to the floods.

The International Federation of the Red Cross and Red Crescent Societies has said the floods could affect 2.4 million people across 16 states.