At least three people, including a child, have died after tornadoes swept through the US state of Oklahoma, authorities said.

Emergency crews are assessing extensive damage to homes and businesses as a result of the high winds, hail and flooding.

Dozens of reported tornadoes have wreaked havoc in America’s Midwest since Friday, with flood watches and warnings in effect on Sunday for Oklahoma and other states – including Kansas, Missouri, Arkansas and Texas.

In Oklahoma, a tornado ripped through Holdenville, a town of about 5,000 people, late on Saturday, killing two people and injuring four others, authorities said. Holdenville is roughly 80 miles from Oklahoma City.

Another person was killed along the Interstate 35 road near the southern Oklahoma city of Marietta, officials said.

Governor Kevin Stitt said: “My prayers are with those who lost loved ones as tornadoes ripped through Oklahoma last night.”

He issued an executive order on Sunday declaring a state of emergency in 12 counties due to the fallout from the severe weather as crews worked to clear debris and assess damage from the severe storms that downed power lines.

Nearly 33,000 customers were without power in Oklahoma as of Sunday morning, according to poweroutage.us, which tracks electric utility outages. In Texas, nearly 67,000 customers were without power.

Significant destruction from the storm was reported in the southern Oklahoma community of Sulphur and well as around Marietta, where a hospital was damaged, according to the Oklahoma Office of Emergency Management.

Residents in other states were also digging out from storm damage. A tornado in suburban Omaha, Nebraska, demolished homes and businesses on Saturday as it moved for miles through farmland and into subdivisions, then slammed into an Iowa town.

Fewer than two dozen people were treated at Omaha-area hospitals, medical staff said.

Neighbouring communities reported a handful of injuries each.

The tornado damage started on Friday afternoon near Lincoln, Nebraska. An industrial building in Lancaster County was hit, causing it to collapse with 70 people inside. Several were trapped, but everyone was evacuated, and the three injuries were not life-threatening, authorities said.

One or possibly two tornadoes then spent around an hour creeping toward Omaha, leaving behind damage consistent with an EF3 twister, with winds of 135-165mph, said Chris Franks, a meteorologist in the National Weather Service’s Omaha office.

Ultimately the twister slammed into the Elkhorn area in western Omaha, a city of 485,000 people with a metropolitan-area population of about one million.

Nebraska governor Jim Pillen and Iowa governor Kim Reynolds spent Saturday touring the damage and arranging for assistance for the damaged communities. Formal damage assessments are still under way, but the states plan to seek federal help.