Fears are growing about outbreaks of disease among up to 2.5 million people affected by floods in Pakistan that have killed up to 1,500 people in the northwest.
Officials warned on Monday that a lack of drinking water is spreading disease, including cholera.
Syed Zahir Ali Shah, the health minister in the Khyber-Pakhtunkhwa province, said
about 100,000 people, mostly children, were suffering from illnesses such as gastroenteritis.
A spokesman for the charity World Vision said teams had visited those affected around the main northwestern city of Peshawar, but that those further north had been inaccessible by road.
"They don't have drinking water or food. They said there have been some visible signs of water-borne diseases," Muhammad Ali told the news agency AFP.
Shoaib Mohammad, a doctor at a 20-bed mobile clinic said he had received patients with trauma, gastroenteritis, skin diseases and dehydration.
Clean water priority
Katy Attfield, the head of disaster management at the British Red Cross, said providing clean water was one of the priorities in the relief efforts.
"With all this water around, it's ironic that clean water isn't always available but that is the case," she told Al Jazeera.
"Sanitation [is a priority] as well. We are trying to prevent any disease outbreaks because it is obviously immediately a concern in situations like this."
The United Nations said 980,000 people had been displaced and that the number would rise over a million when assessments were made in all affected districts.
"A rapid assessment carried out by the UN World Food Programme in four districts - Nowshera, Charsadda, Mardan and Peshawar - puts the figure of people who have lost their homes or are temporarily displaced at nearly 980,000," the UN Office for the Co-ordination of Humanitarian Affairs said.
Survivors have accused the government of failing to provide adequate shelter, food and medicine in the aftermath of the disaster.
Around 300 people blocked a major road in the Nowshera district on Monday to protest at receiving little or no aid.
Hundreds also gathered in Peshawar to protest against the government's slow response.
"I had built a two-room house on the outskirts of Peshawar with my hard-earned money but I lost it in the floods," Ejaz Khan, one of the demonstrators, said.
"The government is not helping us... the school building where I sheltered is packed with people, with no adequate arrangement for food and medicine," the 53-year-old said.
Farhatullah Babar, a spokesman for Asif Ali Zardari, Pakistan's president, told Al Jazeera that survivors had "every right" to criticise the government.
"I think their criticism will persuade the government to do even more than it is doing," he said.
"We really sympathise with those who are marooned and those who have lost lives and relatives. They are justified in criticising because after all, they are the people who are suffering."
Red: Deeply affected
Yellow: Moderately affected
Brown: Flood warning issued
Babar said that the cost of the clean-up may run into billions of dollars. President Zardari has set up a special unit to co-ordinate the response to the disaster and is watching the situation closely as he continues a trip to France.
Al Jazeera's Sohail Rahman, reporting from the Swat Valley, one of the worst-hit areas, said the military and aid organisations were struggling to provide aid.
"There has been some aid from the NGOs and charitable organisations. The military for their part have been flying 24 hours a day with helicopters, trying to get to areas completely surrounded by water, our correspondent said.
"Another storm front is coming in the south of the country. It's expected that an 150,000 people in the Sindh province may be affected between Monday evening and into Tuesday.
"That storm probably will hit the northwest of the country, bringing more chaos to an already devastated region."
The UN has pledged $10m to help in the crisis, and countries including the US, Britain and China have also promised to deliver aid.