Tornadoes that tore through Oklahoma and flattened buildings across one rural town killed at least four people, the US state’s governor Kevin Stitt has said.

Nearly 30,000 people remained without power after tornadoes began late on Saturday night and left a wide trail of destruction.

The damage was extensive in Sulphur, a town of about 5,000 people, where some buildings were reduced to rubble and roofs were sheared off houses across a 15-block radius.

Mr Stitt said about 30 people were injured in Sulphur.

On Sunday, authorities in Iowa said a man injured during a tornado that hit the town of Minden on Friday had died, according to local reports.

Dozens of reported tornadoes have wreaked havoc in the nation’s Midwest since Friday, with flood watches and warnings in effect on Sunday for a handful of states.

“You just can’t believe the destruction,” Mr Stitt said. “It seems like every business downtown has been destroyed.”

In Oklahoma, a tornado ripped through Holdenville, a town of about 5,000 people, late on Saturday, killing two people, and injuring four others, officials said.

Another person was killed along Interstate 35 near the southern Oklahoma city of Marietta, according to the Oklahoma Department of Emergency Management.

In Holdenville, houses were demolished and road signs were bent to the ground in the community roughly 80 miles from Oklahoma City. The sound of chainsaws could be heard in the distance as workers began tackling the damage.

Mr Stitt said in an earlier statement: “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.

More than 30,000 customers were without power in Oklahoma as of midday Sunday, according to poweroutage.us, which tracks electric utility outages. In Texas, nearly 52,000 customers were without power.

In Sulphur, authorities reported unspecified injuries along with significant destruction as the tornado began in a city park before tearing through Sulphur’s central area. Search and rescue operations were under way, according to the Oklahoma Highway Patrol.

Photos from local news media showed several levelled buildings and roofs ripped off of homes. The Murray County Sheriff’s Office urged people to stay away from the city to clear the way for first responders following extensive damage from tornadoes, according to a statement posted by the agency on Facebook.

“Stay home and do not come to look,” the sheriff’s office said.

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

Fewer than two dozen people were treated at Omaha-area hospitals, senior medics said.

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 135-165 mph, 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.