Severe weather warnings have been issued in several states in the central US, after a massive tornado devastated a town in southern Kansas.

Nine people in two counties were killed as the town of Greensburg was hit by a tornado said to be more than a kilometre wide.

An estimated 95% of the town had been destroyed. The city hall, schools, businesses as well as homes were flattened.

The town has been evacuated of its 1,500 residents, who have been instructed not to return while emergency workers search for survivors.

Rescuers are working to reach people trapped in basements and under rubble. Officials say more could be found dead.

Shelters have been set up in nearby towns and National Guard soldiers have been sent to the area to provide security.