Rescue workers and troops in north-west Pakistan struggled today to reach thousands of people affected by the country's worst floods in living memory, as the death toll rose to 800.

Hundreds of homes and vast swathes of farmland were destroyed in the northwest and Pakistani Kashmir, with the main highway to China reportedly cut and communities isolated as monsoon rains caused flash floods and landslides.

The United Nations said almost a million people had been affected by the flooding, and at least 45 bridges destroyed around Khyber Pakhtunkhwa province.

Television footage and photos shot from helicopters showed people clinging to the walls and roof tops of damaged houses as gushing waters rampaged through inundated villages.

Carrying their belongings and with children on their shoulders, some even walked barefoot through the water to seek safety.

‘This is the worst ever flood in the province of Khyber Pakhtunkhwa in the country's history,’ provincial information minister Mian Iftikhar Hussain said.

‘The death toll in floods and rain-related incidents has risen up to 800 across the province,’ he said.

Another 150 people were missing in the north-western province, where many impoverished families live in remote mountain villages.

More than one million people have been affected, the minister said, adding that more than 3,700 houses had been swept away by floods and that the number of homeless people was rising.