Pakistan Indus flood diary - day six
This week, the BBC's Aleem Maqbool is tracing the path of destruction wreaked by Pakistan's recent floods by travelling the length of the country on the mighty Indus river.
In his diary's sixth instalment, Aleem visits the "refugee city" of Sukkur, where new flood victims continue to arrive every day. Aleem will finish his travels in the southern province of Sindh.
DAY SIX: SUKKUR, SINDH PROVINCE
The first major population centre we reached was Sukkur. A few weeks into the crisis, parts of it had been submerged.
The waters have since receded, but Sukkur has become something of a refugee city, taking in the displaced from all the areas around it.
Evidence of the massive movement of people, in this already poverty-stricken region, was everywhere.
All over Sukkur we saw tents pitched up - on cricket grounds, road embankments and even roundabouts.
More than 200 separate camps are estimated to have been established across the district, and schools have been used to give shelter to thousands who were made homeless.
A huge aid distribution centre has been set up here by the UN World Food Programme (WFP).
"The number of people we have had to give assistance to is incredible," says Dorte Jessen, WFP chief officer in Sindh.
"We are talking about serving over a million people from this centre alone, and over seven million people in Sindh."
As access to some towns and villages opens up in areas where the waters are receding, there are people who are leaving Sukkur and trying to get back home.
But with new places along the River Indus being hit, thousands more are still coming here, with whatever belongings they can save.
"We send aid trucks out to help people in one area, but they have to be turned back because the floods reach a new place," says Ms Jessen.
"This is still an evolving disaster. Even three days ago, one million people had to be evacuated from one area."
Not far away, we visited one of the displacement camps, run by the charity Muslim Aid.
We heard stories from some families who had never before left their home village.
Aid workers told us tales of families who had walked so far from their destroyed rural communities that they were scared they had ventured into India.
There are security hazards in northern Sindh, even at the best of times.
Some of those in the camp came from areas where bandits operated and places where there was a risk of looting, and that has also hampered the relief effort, according to Rizwan Baig, Muslim Aid's programme manager in Sindh province.
"There are some places we can't go, especially after dark because of security issues," he says.
"People are dying in those areas, they need our help, but we have to come back to the city because it's too dangerous."
The huge movement of people, the fact the crisis is still developing and the risks involved, are all factors that have led this to be described as the most challenging of aid operations in recent times.