United Nations Secretary-General Antonio Guterres termed the devastations caused by the unprecedented floods "unimaginable" as he visited the affected areas in Sindh and Balochistan on Saturday.

Antonio Guterres, accompanied by Prime Minister Imran Khan, Sindh Chief Minister Murad Ali Shah, Foreign Minister Bilawal Bhutto Zardari and others made an aerial visit to the flood-affected areas today.

On the scale of flood devastations in the country, he remarked "unimaginable".

Reiterating his appeal to help Pakistan cope with catastrophic floods, Antonio Guterres told the developed nations that the international body's help is "a drop in the ocean" compared to what is needed to rebuild.

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 galvanise support for Pakistan, which needs at least $10 billion to repair damaged infrastructure.

The UNSG, in a conversation with journalists in Sukkur, said that there needs to be a serious discussion on loss and damages as "what the UN is doing in Pakistan is a drop in the ocean of what is needed".

"We are perfectly aware of our limited capacity and our resources. But you can absolutely be sure about one thing: were are in total solidarity with the Pakistani people."

The UN chief said that he will ask the international community to ensure that they help Pakistan "now" while vowing to raise awareness about the disastrous situation.

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.

“It is not a matter of generosity, but a matter of justice,” he said, reiterating the UN’s commitment, strong support and solidarity with the flood-affected populace of Pakistan.

Guterres said that huge damages and losses were caused by the floods to human lives and properties.

He stressed that the international community must realise the serious impacts of greenhouse emissions as nature was striking back in the form of natural calamities.

Greenhouse gases have accelerated climate change and the nations with larger greenhouse emission footprints must understand these issues, Guterres added.

Pakistan expects to cut its GDP growth projection for the financial year 2022-2023 to 3% from 5% due to the losses, planning minister Ahsan Iqbal told an earlier news conference.

The United Nations has already launched an appeal for $160 million in aid to help Pakistan cope with the disaster.

In a tweet earlier, the UNSG said developing nations were paying a "horrific price" for the world's reliance on fossil fuels.

"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.

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