A deadly ice storm has struck the central United States, with warnings that more freezing weather is still to come.

Up to 800,000 homes and businesses are without electricity as icy winds wreak havoc with power lines and trees.

Ice up to 1in (2.5cm) thick has covered parts of Oklahoma and Missouri, with more forecast to affect Iowa too.

Accidents on roads made treacherous by driving sleet and ice are to blame for most of more than 20 reported deaths.

A state of emergency has been declared in Oklahoma, freeing up federal resources to help respond to the storm.

Many roads and airports have closed, disrupting people's travel plans - including those of the presidential campaigns.

Forecasters have issued renewed ice storm warnings for parts of Missouri, Kansas, Iowa, Illinois, Wisconsin and Indiana.