United Nations Secretary-General Antonio Guterres said developing nations were paying a "horrific price" for the world's reliance on fossil fuels, as he toured parts of Pakistan hit by floods blamed on climate change.

Nearly 1,400 people have died in flooding that covers a third of the country — an area the size of the United Kingdom — wiping out crops and destroying homes, businesses, roads, and bridges.

Guterres hopes his visit will galvanize support for Pakistan, which needs at least $10 billion to repair damaged infrastructure.

"Pakistan and other developing countries are paying a horrific price for the intransigence of big emitters that continue to bet on fossil fuels," Guterres said in a tweet, shortly before heading to see some of the most flood-affected areas.

"From Islamabad, I am issuing a global appeal: Stop the madness. Invest in renewable energy now. End the war with nature."

Pakistan receives heavy — often destructive — rains during its annual monsoon season, which is crucial for agriculture and water supplies.

But downpours as intense as this year's have not been seen for decades.

'Insanity and suicide'

On Friday Guterres lamented the lack of attention the world gave to climate change — particularly the industrialized nations that scientists blame.

"This is insanity, this is collective suicide," he said.

Pakistan is responsible for less than one percent of global greenhouse gas emissions but is eighth on a list compiled by the NGO Germanwatch of countries most vulnerable to extreme weather caused by climate change.

Guterres is touring flood-hit parts of the south on Saturday, and will also visit Mohenjo-daro, a centuries-old UNESCO-designated world heritage site threatened by the deluge.

Some 33 million people have been affected by the floods, which have destroyed around two million homes and business premises, washed away 7,000 kilometers (4,500 miles) of roads, and collapsed 500 bridges.

The effect of the torrential rain has been twofold — destructive flash floods in rivers in the mountainous north, and a slow accumulation of water in the southern plains.

"If he comes and sees us, Allah will bless him," Rozina Solangi, a 30-year-old housewife from a flooded village near Sukkur, told AFP Friday.

"All the children, men and women are roasting in this scorching heat. We have nothing to eat, there is no roof on our heads. So he must do something for us poor."

The meteorological office says Pakistan received five times more rain than normal in 2022. Padidan, a small town in Sindh province, has been drenched by more than 1.8 meters (71 inches) since the monsoon began in June.

Thousands of temporary campsites have mushroomed on slivers of dry land in the south and west — often roads and railway tracks are the only ground in a landscape of water.

With people and livestock cramped together, the camps are ripe for outbreaks of disease, with many cases of mosquito-borne dengue reported, as well as scabies.