Boy, 12, among six dead as tornadoes hit Michigan and Oklahoma

At least six people have died and more than a dozen others injured after tornadoes struck Michigan and Oklahoma in severe storms that swept across parts of the US.

Officials said four people were killed in southern Michigan, including a 12-year-old boy, and two died in Oklahoma on Friday, with rescue workers continuing to assess the damage.

The storms uprooted trees, brought down power lines, damaged buildings and ripped the roofs off some houses.

The National Weather Service (NWS) said the severe weather could continue into the weekend, warning of thunderstorms and flash flooding from the Great Plains to Texas.

In Michigan, the Branch County sheriff's department said three people were killed and 12 others injured near Union City after a tornado hit on Friday. Power cuts and road closures are expected this weekend, they added.

About 50 miles (80km) away in Cass County, Michigan, authorities reported one death and several injuries.

"Multiple large structures - including homes and pole barns - sustained damage ranging from major structural impacts to complete destruction," they said in a statement.

Hundreds of people were reported to be without power, they added.

Cass County Sheriff Clint Roach announced on Saturday that 12-year-old Silas Anderson had died from unspecified weather-related injuries in Edwardsburg, Michigan.

"Silas was surrounded by family at the time of his passing," the sheriff's office said in a social media post.

Videos shared on social media showed massive whirlwinds sweeping through Union City, and large chunks of debris and dust flying across a car park in the city of Three Rivers.

One local resident described seeing the storm approaching.

"We look out the window and saw the tornado go right down the strip and that's where my daughter is, where my parents, where I live down the road," a Three Rivers resident told the BBC's US partner CBS News.

"I was just very grateful that God protected my daughter and my mom and sister and my family."

Michigan Governor Gretchen Whitmer said she had activated a state emergency for Branch, Cass and St Joseph counties.

"We are working with emergency teams to monitor the situation and co-ordinate resources for those impacted," she said.

"My heart is with the families who lost loved ones and the Michiganders who were injured yesterday."

Emergency management officials said local responders were continuing to search damaged areas and begin recovery efforts.

In Oklahoma, Okmulgee County emergency manager Jeff Moore said a tornado cut an approximately four-mile (6.4km) path of damage to the south of Tulsa.

"We're just getting everywhere as fast as we can, clearing roads as fast we can," Moore said.

Two deaths were reported in Beggs, Oklahoma, according to the Okmulgee county sheriff's office.

Governor Kevin Stitt said he had declared a state of emergency for Alfalfa, Creek, Grant, Major, Okmulgee, Rogers, Tulsa, and Wagoner counties "to ensure Oklahomans have the support and resources they need after last night's storms".