Pakistan scrambled on Tuesday to widen a breach in its biggest lake to prevent it from overflowing amid unprecedented floods that have inundated a third of the South Asian nation, as the United Nations warned of more misery to come.

Flooding, brought by record monsoon rainfall and glacier melt in the north, has impacted 33 million people and killed at least 1,325, including 466 children, the national disaster agency said.

About 636,940 displaced people have been housed in tent villages, it said, adding the raging waters had swept away 1.6 million houses, 5,735 kilometers of roads, railways, 246 bridges, telecommunication systems, 750,000 livestock, and inundated over two million acre of farmland, destroying both standing and stored crops.