Lasker, who works as a video journalist in addition to chasing storms, was filming the aftermath of a tornado system about 100 miles (160km) outside of Chicago when he heard a woman screaming for help.

He was able to help pull the woman's husband from the rubble, saving him, he recounted to a local CBS News outlet.

Lasker was in Streator, Illinois, on Thursday, where tornado were expected to roll through. By the end of the night, at least a dozen reports of tornadoes were documented in Illinois, Indiana and Wisconsin.

When Lasker heard the shouting, he ran over and discovered the woman's husband trapped under what was once their home, he told CBS News Chicago.

The woman used his camera to continue filming as he started trying to pry her husband from the rubble, he told the outlet.

"I gave him a little comfort and then the police showed up," Lasker said, adding that officers ultimately were able to free him.

The tornadoes began on Thursday afternoon, local time, in the Midwest region of the US.

Streator, where Lasker rescued a man, was among the most heavily hit areas.

Mayor Tara Bedei said no deaths were reported in the city of about 12,000, but video shows the town has extensive damage.

Outside of the damage, hundreds of thousands of people were left without power.

Air traffic controllers at Chicago's Midway Airport had to evacuate their tower because of a tornado warning, and thousands of flights were delayed or cancelled.

And in Chicago, the MLB game between the White Sox and the Atlanta Braves was postponed because of the severe weather.

The preliminary assessment of the number of tornadoes in the US during May is 168, according to the National Oceanic and Atmospheric Administration (NOAA). (BBC)