As many as 30 people are reported killed after a tornado tore through the city of Joplin in the US state of Missouri, officials say.
The town suffered a "direct hit" from the tornado and parts of the city have been devastated, local media says.
Missouri Governor Jay Nixon has declared a state of emergency and warned that more storms are on the way.
Last month tornadoes and storms killed at least 350 people in Alabama and six other southern states.
Fierce storms ripped through several Midwestern states, and officials fear at least 24 people are dead while an unknown number are injured and trapped by a "three-quarter to one mile wide, three-mile long" tornado that touched down in Joplin, Mo.
Missouri Gov. Jay Nixon declared a state of emergency Sunday evening and activated the Missouri National Guard in response to the destruction the storm left in its wake.
In Joplin, St. John's Regional Medical Center was fully evacuated after it took a direct hit from the tornado, and seven people have been reported dead at a local nursing home, according to police reports.
State and local law enforcement agencies, including fire mutual aid, are coordinating search and rescue and recovery operations. The Missouri State Highway Patrol sent troopers from other regions to help local officers in southern Missouri deal with the destruction, according to a statement from a Missouri Governor's official.
"These storms have caused extensive damage across Missouri, and they continue to pose significant risk to lives and property," Nixon said. "As a state, we are deploying every agency and resource available to keep Missouri families safe, search for the missing, provide emergency medical care, and begin to recover."
Federal Emergency Management Agency Region VII set up a response coordination center and sent a liason team to the Missouri state emergency communications center, according to a FEMA official.
"Basically it's an all out effort to get all of the most important resources available for this type of situation down as soon as possible," a state emergency management spokesperson said.
Phone communications in and out of the city of about 50,000 people about 160 miles south of Kansas City were largely cut off.
President Obama released a statement on the emergency late Sunday night.
"Michelle and I send our deepest condolences to the families of all those who lost their lives in the tornadoes and severe weather that struck Joplin, Missouri as well as communities across the Midwest today. We commend the heroic efforts by those who have responded and who are working to help their friends and neighbors at this very difficult time," Obama said in the statement.
"At my direction, FEMA is working with the affected areas' state and local officials to support response and recovery efforts, and the federal government stands ready to help our fellow Americans as needed," he added.
Earlier Sunday, tornadoes had torn across other parts of the region, killing at least one person in Minneapolis.
Tornado warnings and watches were posted from Texas to Michigan.
Storms Rattle Midwest
Midwest residents were cleaning up Sunday after several tornadoes Saturday left one man dead and one Kansas town nearly destroyed.
At least 20 tornadoes were reported across three states Saturday: 14 in Kansas, 5 in Oklahoma, and 1 in Missouri.
In the small town of Reading, Kan., twisters ripped through the area and left more than 20 homes destroyed and 200 more damaged.
"Lots of damage all over town, the farther south in town the more damage there is. Lots of trees down, large trees, there's buildings that have been totally devastated," said Coffee County Emergency Coordinator Russel Stukey.
One fatality and several injuries were reported in connection with the twisters, according to authorities.
"Everything is destroyed. We're going to have to stay strong for the community," said one resident told Kansas City ABC News affiliate KMBC.
Power was knocked out Saturday and roads in and out of area were closed, KMBC reported.
According to Sharon Watson with the Kansas State Division of Emergency Management, there was also hail as large as a baseball reported throughout northeast part of the state.
"We've been fortunate so far to not have as much damage as we have seen in the past, such as the year 2007 when the town of Greensburg was basically destroyed, a town of 1,500," Watson said.
Kansas Governor Sam Brownback declared a state of emergency for at least 16 counties.