At least four people were killed in the US state of Oklahoma and thousands left without power after tornadoes began late Saturday night, health authorities said on Sunday.

A four-month-old child was among those killed, authorities said. Sulphur, a town of about 5,000 people south of Oklahoma City, appeared to have taken the biggest hit.

"My prayers are with those who lost loved ones as tornadoes ripped through Oklahoma last night," Governor Kevin Stitt (Republican) said in a statement.

One hospital was damaged and a major highway at the border with Texas was closed "due to overturned vehicles and power lines across the highway," said the Oklahoma Office of Emergency Management.

Dozens of houses were destroyed and tens of thousands of people were left without electricity across the state. Hospitals across the state reported about 100 injuries, according to the Oklahoma Department of Emergency Management.

In Murray County, in Oklahoma's south, authorities urged people to stay away from the city to clear the way for first responders. "Stay home and do not come to look," the sheriff's office said.

State of emergency in 12 Oklahoma counties

Governor Stitt declared a state of emergency in 12 counties hit by the severe storm, as crews worked to clear the debris and assess the damage.

Despite multiple storms, some parts of Oklahoma were suffering from drought. 

"Several rounds of thunderstorms dumped excessive amounts of rain yesterday and early this morning. Unfortunately, far northwest Oklahoma missed out on the rain where moderate to severe drought is occurring," an Oklahoma weather service said. 

Biden declares major disaster

In a call with Governor Stitt, US President Joe Biden offered the full support of the federal government in order to aid any recovery efforts, the White House said in a statement.

Biden also declared a major disaster over the severe storms that flooded the states of Washington and Kansas, the White House said.

Storm watch in effect across Midwest

Severe storms and tornadoes have wreaked havoc across the Midwest since Friday.

On Friday alone, 78 tornadoes were reported, mostly in Nebraska and Iowa. Another 35 were reported on Saturday from northern Texas to Missouri.

As of Sunday 17:20 UTC, the National Weather Service had active flood watches and warnings for several states in the region, including Oklahoma, Kansas, Missouri, Arkansas and Texas.

Although tornadoes are usual for the region in the spring, meteorologists say separate major outbreaks in succeeding days is rare.

rm, fb/dj (AP, dpa, AFP)