Nearly a million children have been "severely affected" by a severe earthquake in Nepal that has killed more than 3,200 people, a spokesman for the United Nations Children's Fund (UNICEF) said, as rescue and aid workers struggle to cope.

With hundreds of thousands of Nepalis sleeping out in tents or in the open, UNICEF said its relief workers were watching for waterborne and infectious diseases.

A shoe lies among the debris of a collapsed house a day after an earthquake in Bhaktapur, Nepal April 26, 2015. | REUTERS photo

"What we know that at this point is there are nearly a million children who are severely affected. Our biggest concern for them right now is going to be access to clean water and sanitation, we know that water and food is running out," UNICEF's Christopher Tidey said by telephone.

A total of 3,218 people were confirmed killed (toll noted at 2pm) in Saturday's 7.9 magnitude quake, a police official said on Monday, the worst in Nepal since 1934 when 8,500 died. More than 6,500 were injured.

Feature image source: REUTERS