Ahsan Iqbal says the world has an obligation to help the South Asian nation cope with the effects of man-made climate change.

Unprecedented flash floods caused by historic monsoon rains have washed away roads, crops, infrastructure and bridges, killing at least 1000 people in recent weeks and affecting more than 33 million, over 15 per cent of the country's 220 million population.

The climate change minister has called the situation a "climate-induced humanitarian disaster of epic proportions".

"I think it is going to be huge. So far, (a) very early, preliminary estimate is that it is big, it is higher than $US10 billion," Iqbal said in an interview.

"So far we have lost 1000 human lives. There is damage to almost nearly one million houses," Iqbal said at his office.

"People have actually lost their complete livelihood."

Iqbal termed the recent floods worst than the 2010 disaster in Pakistan, for which United Nations had issued its largest disaster appeal.

The minister said it might take five years to rebuild and rehabilitate the nation, while in the near term it will be confronted with acute food shortages.

Social media users have posted videos showing stranded people and whole families washed away by floodwater.

Southern, southwestern and northern Pakistan have been the hardest hit by the floods, which have swept large swaths of farmland and stored crops, also isolating the regions from rest of the country for the last several days.

Tens of thousands of families have left their homes for safer places, moved in with their relatives, or to state-run camps, while others have been spending nights in the open, waiting for any help, such as tents, food and medicine.

Pakistan has appealed for international help and some countries have already sent in supplies and rescue teams.

The nation's foreign minister said on Sunday he hoped financial institutions such as the International Monetary Fund would provide financial aid, taking the economic cost of the floods into account.

However, Iqbal said any formal requests for financial help would need to wait until the entire scale of the damage was known, something Pakistan was now evaluating with partners, including the World Bank and the Asian Development Bank.

Iqbal also said the world owed Pakistan, which was a victim of climate change caused by the "irresponsible development of the developed world."

"Our carbon footprint is lowest in the world," he said.

"The international community has a responsibility to help us, upgrade our infrastructure, to make our infrastructure more climate resilient, so that we don't have such losses every three, four, five years.

"Those areas which used to receive rainfall aren't receiving rainfall and those areas which used to receive very mild rains are receiving very heavy rainfall."

Australian Associated Press