Barack Obama, the US president, has visited the tornado-devastated southern state of Alabama where more than 300 people have been killed in days of storms.
Obama toured the city of Tuscaloosa on Friday, visiting neighbourhoods where trees had been uprooted and houses destroyed and told local residents: "We're going to make sure you're not forgotten."
"We just took a tour and I've got to say, I've never seen devastation like this," said Obama during his Alabama visit. "We were just talking to some residents who were lucky enough to escape alive but have lost everything."
Earlier, Obama received an update on the disaster from Janet Napolitano, the homeland security chief, and other officials as people in seven affected states come to terms with scenes of utter devastation.
Becoming the deadliest storms in the US since Hurricane Katrina in 2005, the violent weather has left thousands of people homeless and millions more without electricity.
Obama has declared a state of emergency in Alabama, the hardest-hit state. He also vowed to mobilise the federal government's resources to help the storms-ravaged region.
"While we may not know the extent of the damage for days, we will continue to monitor these severe storms across the country and stand ready to continue to help the people of Alabama and all citizens affected by these storms," Obama said in a statement.
The president's action makes federal funding available to affected individuals in storm-ravaged areas.
Assistance can include grants for temporary housing and home repairs, low-cost loans to cover uninsured property losses, and other programmes to help individuals and business owners recover from the effects of the disaster.
More than 131 people have been killed in Alabama alone and Robert Bentley, the state governor, has described "massive destruction of property".
"We expect [the death toll] to rise," Bentley said, adding that six million people were still without power.
The clusters of powerful tornadoes - more than 160 in total - combined with storms cut a swathe of destruction heading from west to east over several days.
In preliminary estimates, other state officials reported 32 killed in Mississippi, 30 in Tennessee, 11 in Arkansas, 14 in Georgia, eight in Virginia and two in Louisiana.
Some of the worst devastation occurred on Wednesday, when a 1.6km-wide tornado slammed into Tuscaloosa, home to 95,000 people, killing at least 37 people including some students.
Tornadoes are a regular feature of life in the US South and Midwest, but they are rarely so devastating.
Al Jazeera's John Terrett, reporting from Birmingham, Alabama, said that electricity and water had been cut off and the city was a scene of devastation.
Adrienne Veilleux, Accuweather meteorologist, told Al Jazeera: "Severe weather season in the United States does generally run from April until June, so it's not unusual to see strong thunderstorms.
"However, the number of thunderstorm reports with hail, the damaging winds and even tornadoes, is a bit unusual."
Floods were a big concern throughout the storm-hit area, where rain compounded with melted snow caused rising rivers and saturated soils.
The storms forced the Tennessee Valley Authority to close three nuclear power plants in Alabama and knocked out 11 high voltage power lines.
Violent weather has pummelled much of the US South this month. Two weeks ago, at least 47 people died as storms tore a wide path from Oklahoma to North Carolina.
"This year has been quite bad already. We have already seen over 700 reports just within the month of April, and this is actually record breaking," Veilleux added.