Officials in Washington County, Ill., said an elderly brother and sister were killed when a twister slammed into their farmhouse in Nashville, Ill., near St. Louis, the Chicago Tribune reported.
County Coroner Mark Styninger said the body of Joseph Hoy, 80, was found in a field near his home.
"His house was blown away by a tornado," Styninger said. "He suffered massive trauma."
The body of Hoy's 78-year-old sister Frances was found under debris from the house.
The newspaper said Patti Thompson with the Emergency Management Agency said two people, whose names weren't available, were killed in Massac County in southern Illinois.
The fifth fatality was an unidentified person in Washington Township in Tazewell County.
The Tribune said dozens of other people were reported injured.
"We have extensive damage, we have homes that have been demolished," Sara Sparkman, a spokeswoman with the Tazewell County Office of Emergency Management, told the Tribune. "We have heard of neighborhoods that have one or two houses left standing that people can go back to, the rest there is nothing left of them.
"We have power lines down, we have phone disruptions, it's extensive in Tazewell County."
CNN reported storms destroyed at least 70 homes in two Illinois communities and rescuers were trying to reach residents trapped in their basements. The National Weather Service said more than 60 tornadoes had been reported in the Midwest.
The severe weather was creating a "particularly dangerous situation" across the region, a U.S. forecaster said Sunday.
"A particularly dangerous situation is unfolding across the Midwest where the stage is set for devastating tornadoes," Accuweather.com reported. The forecaster said severe thunderstorms and tornadoes will spread eastward across the lower Great Lakes and Ohio Valley through Sunday evening.
CBS News reported more than 75,000 people in the Chicago area were left without power late Sunday, and the central Illinois community of Washington appeared particularly hard-hit.
A slew of tornadoes touched down in the U.S. Midwest, causing the Chicago Bears' game against the Baltimore Ravens to be suspended. The game was resumed later Sunday afternoon.
The game was suspended late in the first quarter at Soldier Field and fans were told to seek cover in the nearest covered concourse.
The storm spurred tornadoes, some of which touched the ground, throughout northern, eastern and central Illinois, southeastern Wisconsin, Indiana, Kentucky and southwestern Michigan, Accuweather reported.
The National Weather Service confirmed a tornado touched the ground near Coal City, Ill., moving northeast at 55 mph. The service called the situation "life threatening" and ordered residents in the vicinity to "take cover now." The alert was in effect through 1 p.m. local time.
Confirmed tornado touchdowns in the Peoria, Ill., area resulted in no injuries, Ernie Goetsch, of the National Weather Service, said, though a television cell tower at WEEK-TV was knocked down.
A tornado watch was in effect until 4 p.m. local time for all of the Chicago metropolitan area and parts of southeast Wisconsin, and Flightstats.com reported more than 400 flights were delayed and 140 were canceled due to Sunday's storms.
About 3,500 customers in South Milwaukee, Wis., were without power Sunday morning due to the storms, the Milwaukee Sentinel Journal reported. The Milwaukee County Sheriff's Office also reported flooding throughout the city.
The storms, which have also produced wind gusts of up to 75 mph, were expected to spread across the Northeast Sunday night into Monday, Accuweather reported.
The Tribune said the towns of Washington and Pekin were hit hard, with entire blocks leveled in Washington.
Grundy County Board Chairman Ron Severson said a curfew was put in place from 8 p.m. to 6 a.m.in a subdivision in the town of Diamond to reassure residents concerned about the possibility of looting.
Kristen Johnson, a spokeswoman for OSF Saint Francis Medical Center in Peoria, said the hospital treated 37 people injured by storms.
"We anticipate the worst is over," said Johnson.