The airport in the US city of St. Louis was expected to resume most of its operations Sunday after tornadoes and high winds tore through the Midwestern city, cutting a swath of destruction.

Lambert-St. Louis International Airport was to reopen at about 70 percent capacity after restoration of power and clearing the debris, authorities said.

Richard Bradley, president the St. Louis Board of Public Service, said it was too early to give a damage estimate for the airprort, but the losses were clearly in the millions of dollars.

Five people were hospitalized late Friday after being hurt by flying glass when the storms ripped off the roof of the main terminal and blew out windows and doors.

"All operations are closed here today and there are no flight activities until assessments can be made of the damage and what it will take to make the facility safe enough to resume flights," airport spokesman Jeff Lea told AFP.

The National Weather Service said the tornado that shook the airport and its nearby suburbs ranked as a minimum EF4 storm on the one-to-five Enhanced Fujira tornado-strength scale.

The rating meant the tornado had caused "extreme damage" that had completely leveled solid and whole frame houses, with winds of up to 200 miles (320 kilometers) per hour.

Airport director Rhonda Hamm-Niebrugge told reporters the five injured people have been released from hospital after treatment.

"When you look at the devastation around, it really is a miracle that there were no fatalities and certainly very minor injuries. So, we're grateful for that," she added.

The storms, and an apparent tornado, struck the airport in the early evening Friday, forcing airport officials to herd hundreds of travelers into safer areas.

"We had a vacuum effect, when the wind sucked anything that moved down the concourse," Lea said. The main terminal suffered much damage, with part of its roof ripped off, and half of the windows of Concourse C were blown out.

Staff spent the night mopping up, but the airport, which handles more than 15 million passengers a year, was still running on its back-up generators on Saturday. The runways were scattered with debris, such as crushed cars and wrecked signs, while nearby houses had been ripped apart.

Carl Lawrence was standing by the baggage carousel area when the strong wind hit. "It rushed through the door and threw everybody against the wall," Lawrence told the St. Louis Post-Dispatch.

Missouri Governor Jay Nixon has declared a state of emergency as officials reported some injuries and widespread damage in neighborhoods around St. Louis.

"The state of Missouri is ready to assist at every stage of this emergency to keep Missouri families safe and help communities recover," Nixon said in a statement.

Fire officials said about 50 homes in a subdivision just off the Airport Road were damaged. No one was hurt but several people had to be helped to escape their damaged homes.

"It was boom, boom, boom," Alicia Braggs said, recalling the storm. "It seemed like there was some kind of terrible pressure on my roof, and I could feel the wind."

The National Weather Service has also issued flood warnings for the area, saying the heavy rains will likely cause rivers to burst their banks.

Powerful tornadoes struck several southern and central US states earlier this month, killing 44 people and reducing whole neighborhoods to rubble.