Myanmar's president has called for the evacuation of low-lying areas as the Irrawaddy river threatened to breach embankments, leaving villagers with just sandbags to hold back churning waters that have hit much of the country.

Floods from a heavy monsoon season have cut through swathes of South and Southeast Asia in recent weeks, claiming hundreds of lives and displacing millions.

Twelve of Myanmar's 14 regions have been struck, with officials saying 74 people have been killed and more than 330,000 affected - many forced into monasteries and other makeshift shelters after their homes were flooded.

Relief agencies said floods had receded in some northern and western areas, allowing supplies of food and clean water to trickle in, although landslides were still a threat.

The centre and south are now bracing for floods as water drains through the vast Irrawaddy delta.

Immediate danger

In a message broadcast on radio early on Thursday, President Thein Sein said areas near the Irrawaddy were at risk as the river rises "above danger level".

"As we cannot prevent natural disasters, I urge fellow citizens to move to safer places ... it's the best way," he said, adding Hinthada and Nyaung Don townships along the river were in immediate danger.

In Hinthada, the army helped residents prepare for floods, securing belongings inside homes and reinforcing embankments with sandbags, with villages on the other side of the barriers already submerged up to their roof-tops.

International aid efforts have buttressed the response of the army and local communities, following a rare appeal by the government for outside help.

But thousands of people are still feared stranded in rugged and remote Chin State after days of rain caused flash floods and landslides that swept away homes, roads and bridges.