Families waded through water and cattle were loaded onto boats in a mass evacuation of around 100,000 people in Pakistan's Punjab province, officials said Wednesday.
Several hundred villages and thousands of acres of cropland in the central province were inundated when the Sutlej river burst its banks on Sunday.
"The flood waters came a couple of days ago and all our houses were submerged. We walked all the way here on foot with great difficulty," 29-year-old Kashif Mehmood, who fled with his wife and three children to a relief camp, told AFP on Tuesday.
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Rescue boats travelled from village to village over the past several days, collecting people forced to wait on the roofs of their homes as the water level rose around them.
Others pushed their motorcycles through shallower waters or held belongings above their heads until they found dry ground.
"There is five or six feet (1.5-1.8 metres) of water accumulated over the roads," Muhammad Amin, a local doctor volunteering at a relief camp, told AFP on Tuesday.
"The only route that could have been used to come and go is now underwater. This 15- or 16-kilometre route is now being covered by boat so that we can rescue people."
Muhammad Aslam, Pakistan's chief meteorologist covering floods, said the river level was at its highest in 35 years.
"We have rescued 100,000 people and transferred them to safer places," Farooq Ahmad, spokesman for the Punjab emergency services, told AFP on Wednesday.
Shared monsoon burden
The head of Punjab's government, Mohsin Naqvi, said that monsoon rains had prompted authorities in India to release excess reservoir water into the Sutlej river, causing flooding downstream on the Pakistani side of the border.
India has seen severe monsoon rains this year, with more than 150 killed in rain-related incidents since July.
Ali Tauqeer Sheikh, a climate and water expert based in the Pakistani capital Islamabad, said the water levels in the Sutlej river had become so high that they were beyond India's storage capacity.
"There was no intention or maliciousness on the part of India. The water had to eventually flow downstream to Pakistan," he told AFP.
"Because in Pakistan we were monitoring the Indian monsoon quite closely, we were expecting and anticipating it, and therefore Punjab and Pakistani authorities had enough warning time to evacuate communities and to plan emergency response," he said, adding that both countries were facing a climate disaster.
Indian authorities did not respond to requests for comment.
The summer monsoon brings South Asia 70-80 percent of its annual rainfall between June and September every year.
It is vital for the livelihoods of millions of farmers and for food security in a region of around two billion people -- but it also brings landslides and floods that lead to frequent evacuations.
More than 175 people have died in Pakistan in rain-related incidents since the monsoon season began in late June, mainly due to electrocution and buildings collapsing, emergency services have reported.
Pakistan was devastated by weeks of unprecedented floods last year that inundated nearly one-third of the country, but the central province of Punjab was largely spared the worst of the impact.
Large parts of Sindh and Balochistan are still recovering from the damage.
The Punjab Disaster Management Agency has warned that forecasted monsoon rains could exacerbate the flooding in the coming days.
Scientists have said climate change is making seasonal rains heavier and more unpredictable.
Pakistan, which has the world's fifth-largest population, is responsible for less than one percent of global greenhouse gas emissions, according to officials, but is highly vulnerable to extreme weather exacerbated by global warming.