Tornadoes kill two in Oklahoma as state of emergency declared in 12 counties

A partially torn off roof is seen on a damaged home in Omaha, Nebraska (Chris Machian/Omaha World-Herald via AP)

At least two people, including a child, have died after tornadoes swept through the US state of Oklahoma, authorities said.

Emergency crews are assessing extensive damage to homes and businesses as a result of the high winds, hail and flooding.