Media playback is unsupported on your device Media caption Aerial footage shows the extent of the devastation caused by tornadoes in Hattiesburg, Mississippi

Severe weather killed at least 21 people in the US South and injured many more, emergency officials say.

Weather officials warn of high winds, rain and flash flooding as the weather system now moves up the east coast.

Four people were killed in Mississippi and 16 in Georgia during the weekend's deadly tornadoes and thunderstorms.

President Trump has pledged federal assistance to the three states that have been most-affected by the severe weather.

"The tornadoes were vicious and powerful and strong and they suffered greatly," Mr Trump said on Sunday at the White House.

"So we'll be helping out," he added.

The National Weather Service said 39 possible tornadoes were reported over the weekend.

Thunderstorms and tornadoes battered Georgia on Sunday, leaving 16 people dead, according to a tally by the Storm Prediction Center in Oklahoma.

Most of the deaths occurred in Cook County, where a mobile home park was apparently struck by a tornado, according to the Georgia Emergency Management Agency.

Image copyright EPA

Image copyright EPA Image caption Ann Bell stands in the foundation of her son's mobile home, which was lifted in the air by a tornado

Cook County coroner Tim Purvis said numerous mobile homes had been "levelled" before dawn on Sunday in the park near the city of Adel.

Emergency teams are still searching for survivors beneath the rubble, he added, and by Monday evening, residents had not been permitted to return.

Mr Purvis estimated that the park has about 40 mobile homes in total, and roughly half were destroyed.

"These storms have devastated communities and homes in South Central Georgia, and the state is making all resources available to the impacted areas," Governor Deal said in a statement.

"Trailers are just flat, just laid on top of people", rescue worker Debbie Van Brackel told the Atlanta Journal-Constitution.

"You need a bulldozer to pull it off. Trailers are upside down."

Image copyright EPA Image caption Seven of the deaths were reported outside Adel, in Georgia

Image copyright EPA Image caption A state of emergency was declared in seven Georgia counties

In Brooks County, coroner Michael Miller said two people died when an apparent tornado tossed a mobile home around 100 yards into the middle of Highway 122.

Swathes of the south-eastern United States have been hit by storms over the weekend.

Several tornadoes were also reported in South Carolina and Florida, officials say.

A woman died in northern Florida after a tree crashed into her home as a thunder storm swept through the area.

Media playback is unsupported on your device Media caption Footage showed the destruction caused by a tornado in southern Mississippi

In southern Mississippi, four people died in the path of a tornado with winds above 218 km/h (136 mph).

More than 50 others were injured and about 1,100 homes were damaged or destroyed, state officials said.

The Georgia Emergency Management Agency issued advice on the best and worst places to shelter from a tornado late on Saturday, advising locals in the path of a tornado to cover themselves with blankets or a mattress for protection.