Urgent aid appeal launched as satellite images show a third of Pakistan underwater

The floods have claimed more than 1,100 lives, including 399 children, destroyed more than a million homes and swept away crops, livestock and major infrastructure such as roads and bridges.

Aid workers are battling immense logistical challenges to get to millions of people in need, particularly in south-eastern Sindh province where the water level remains high. Even in areas where the water has slightly receded, aid distribution is complicated by damaged roads, cut power lines and blocked railways.

Speaking from the north-western Khyber Pakhtunkhwa province, Ahmad said he had been in the country for the 2010 floods, which killed nearly 2,000 people, but this was worse.

Another humanitarian worker on the ground, Ajeeba Aslam, of HelpAge International, said 2.3 million of the 33 million people affected are believed to be elderly, and deemed particularly vulnerable as they are often unable to reach makeshift camps for the displaced.

The Pakistani government has said the damage from the floods could total around $10bn (£8.6bn), and has implored the world to help as it struggles to cope with the impact of a climate crisis it did little to create.

Appeals will be broadcast on the BBC, ITV, Channel 4, Channel 5 and Sky on Thursday following their evening news bulletins.