Thousands of people displaced by fighting in northwest Pakistan are desperately in need of medicines to treat ailments such as chronic diarrhea, urinary and respiratory tract infections and scabies, aid agency Merlin said on Thursday.

The Pakistani military offensive against Taliban militants in the former tourist region of the Swat valley has forced at least 830,000 people from their homes and sparked a major humanitarian crisis with relief organisations scrambling to meet the needs of displaced populations.

"Some of the people fleeing from the fighting have walked over 50 km (31 miles) to get to the camps," Patrick Parsons, Merlin's operations controller, told AlertNet by telephone.

"We are treating people for various ailments caused by lack of water, poor sanitary conditions and also due to the dust and heat."

Parsons said most of the displaced were coming from higher grounds where they were accustomed to lower temperatures and access to clean water sourced from mountain springs.

"The conditions in the areas where people were fleeing to are very different from what they are used to," he said.

"People now have to deal with temperatures as high as 40 degrees Celsius (104 degrees Fahrenheit) and water which is not as good quality as they had before."

The region has been under a curfew for days, but the military has twice relaxed the curfew to let people flee. This has resulted in a mass exodus into towns and camps in neighbouring districts.

The U.N. refugee agency said it has registered more than 670,000 displaced from the latest fighting, but it is believed up to 200,000 people have not registered.

Parsons said one of the biggest concerns was of a malaria outbreak in Mardan district, where hundreds of thousands have sought refuge in camps and with host communities.

The Swat valley is free of malaria due to its higher altitude, said Parsons, adding that most of the displaced people did not have a natural immunity to disease.

Merlin is trying to serve the needs of IDPs in Jalala and Sheikh Shehzad camps in Mardan as well as to thousands who are living with relatives, friends and also renting accommodation.

But Dr Riaz Nasrullah, responsible for Merlin's activities in the North West Frontier Province where the fighting is taking place, said that the scale and speed with which the crisis was unfolding has left the agency struggling to meet demands for medicines.

"We urgently need antibiotics, analgesics, multivitamins, oral rehydration solutions and medicines in the form of syrups for children," he said.

The United Nations has warned of a protracted humanitarian crisis for a country already being propped up by a $7.6 billion International Monetary Fund loan.

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