Tens of thousands of people in Pakistan have been forced to flee their homes following deadly floods, as the country’s prime minister warned the “magnitude of the calamity is bigger” than expected.

Nearly 1,000 people have been killed in the floods since mid-June, which have been triggered by heavy monsoon rains.

The latest destruction saw a major bridge destroyed overnight, cutting off some districts from road access, in the northern province of Khyber Pakhtunkhwa.

Pakistan’s Prime Minister Shehbaz Sharif, who was filmed in a helicopter dropping relief to flood-hit areas, tweeted that “the magnitude of the calamity is bigger than estimated”.

“Times demand that we come together as one nation in support of our people facing this calamity,” he wrote.

The country’s climate change minister, Sherry Rehman, has called the situation a “climate-induced humanitarian disaster of epic proportions”.

Fears of flooding has prompted around 180,000 people in the district of Charsadda to flee their homes, according to officials.

Some spent the night on highways with their livestock.

More than 30 million people in Pakistan have been affected by the historic monsoon rains and flooding over the last few weeks, Ms Rehman has said.

The military is helping with the response to the floods, while Pakistani leaders plan to launch an international appeal fund.

In neighbouring Afghanistan, the Taliban has appealed for help after flooding in central and eastern provinces.

The death toll from floods this month in Afghanistan had risen to 192, disaster authorities said.

Thousands of livestock had been killed and 1.7 million fruit trees destroyed, raising concerns over how families would feed themselves going into the cooler months while the country deals with an economic crisis.