At least 12 people have been killed by a storm system in the US Midwest that brought devastation to parts of Illinois, Missouri and Kansas.

Three people died in Tennessee hours after reports of deaths in Illinois and in Missouri.

More than 100 were hurt and buildings badly damaged across multiple states, with at least 16 tornado sightings.

The theatre next to me kind of exploded - it went everywhere John Moore, Witness In pictures: Midwest tornadoes

Rescue workers are searching for survivors trapped in wrecked homes, including a trailer park near Buffalo.

Kansas Governor Sam Brownback and Missouri Governor Jay Nixon have declared a state of emergency.

It is not clear if the reported tornados were the cause of the deaths in Tennessee.

'Major destruction'

The mayor of Harrisburg, Illinois, Eric Gregg, told CNN: "We've got homes toppled, cars thrown in lakes. You can't imagine how devastating it is until you're there."

"In small communities it's just heart-breaking - we all know each other, we all care very much about each other."

He added that he was optimistic that rescue teams would be able to find survivors.

In Missouri, the towns of Branson, Buffalo, Cassville, Lebanon and Oak Ridge suffered extensive damage.

In downtown Branson, Missouri, a country music hub, debris and scattered road signs littered the streets.

One witness, John Moore, who owns a diner damaged in the storm, said a twister rampaged down the main street, appearing to "jump side to side".

"The theatre next to me kind of exploded. It went everywhere. The hotels on the two sides of me lost their roofs. Power lines are down. Windows are blown out," he added.

"There's major, major destruction. There has to be millions dollars of damage all down the strip."

Branson is about 110 miles (177km) from Joplin, where a deadly tornado in May 2011 killed 161 people.

The tornadoes are said to have been generated by a cold storm moving down from the Rocky mountains that hit a warm front as it moved east, said Corey Mead, lead forecaster at the US Storm Prediction Center, Oklahoma.

Sixteen twisters were sighted in the US states of Nebraska, Kansas, Missouri, Illinois and Kentucky.

Tornado season begins in March, but correspondents say twisters are not unusual earlier in the year.