Hundreds of thousands of people are fleeing flash floods after being warned to evacuate as the death toll from severe monsoon rains in Pakistan and neighbouring India climbed to 457 people.
Ahmad Kamal, spokesman for the National Disaster Management Authority, said the Chenab River breached an embankment early today following a warning the day before.
The floods, which began in the Himalayan region between the two countries on September 3, have flowed down to the plains, affecting more than 1.5 million people in Pakistan.
The deluge is the worst since 2010, when some 1,700 people died in flooding in Pakistan.
The Chenab River breach could be a 300ft wide breach, Pakistani minister for water and power Khwaja Mohammad Asif told the country's parliament.
"We have so far breached it only 100 feet." He had said on Tuesday that the breach could cause nearly 700,000 to leave their homes.
Five more districts could be at risk from the flooding, said Mr Kamal.
Pakistani and Indian troops have been using boats and helicopters to drop food supplies for stranded families and evacuate victims. However, the challenge of the situation grows as more than 1.5 million people are now affected as the rushing waters have destroyed the homes of thousands of families.
The floods have triggered landslides in the divided Kashmir region, split between the two rivals, and caused much devastation in northern and eastern Pakistan.
The rains washed away houses, bridges, communication equipment and crops. Pakistani and Indian troops say they have evacuated nearly 75,000 people.
Others have waded through waist-deep water to escape the floods, as women carried household items and children on their shoulders as others dragged their livestock along. Hundreds of others remain stranded on the rooftops, waving for help to every passing helicopter.
"We are focusing more on women, elderly people and children," said a rescue official in the Jhang district.
"I have lost everything," said Haleema Bibi, 65, while weeping after she got off a boat. Her granddaughter was scheduled to get married in some days, she said, whose dowry the water has swept away. She appealed to the rescuers to go back to her village again where her grandson was still stranded.
So far, 257 have died in Pakistan and Pakistan-administered Kashmir and at least 200 people have been killed in India, officials said.
In Pakistan, the floods are now moving south, said Mr Kamal.
The inundated Kashmir region in the northern Himalayas is divided between India and Pakistan and claimed by both. Two of the three wars the countries have fought since their independence from Britain in 1947 have been over controlling it.
Both nation's armies airdropped relief packages to victims that included blankets, food supplies, medicine and drinking water.
In aerial shots of Srinagar, the main city in the Indian-controlled Kashmir, it looked like a giant, muddy lake with only the tops of inundated houses visible. Scared survivors clung to tree tops and waited for rescue helicopters to save them.
Tempers were also running high over rescue efforts from the worst flooding.
In one neighbourhood angry survivors heckled a former government minister and got into scuffles with some rescue workers as anxiety about thousands still missing or unaccounted for grew.
"They are asking for bribes to rescue us," said one man shaking with rage.