At least six dead after tornadoes sweep across Michigan and Oklahoma, officials say

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 and two died in Oklahoma on Friday, with rescue workers continuing to assess the damage.

The storms uprooted trees, downed power lines, damaged buildings and ripped the roofs off some houses on Friday.

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 were injured near Union City after a tornado hit on Friday. Power outages and road closures are expected this weekend, they added.

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

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.

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

"We are working with emergency teams to monitor the situation and coordinate 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 are continuing to search damaged areas and begin recovery efforts.

In Oklahoma, Jeff Moore, the county's emergency manager, said a tornado cut around a 4-mile (6.4 km) path of damage in Okmulgee county, some 30 miles (48 km) 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.

Oklahoma Governor Kevin Stitt said he 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".