Footage has emerged of a US National Guard cargo plane crashing onto a busy highway in Georgia moments after taking off from a nearby airport.

The plane narrowly missed people on the ground but killed at least nine passengers.

An orange and black fireball rose into the sky after the Air National Guard C-130 crashed onto state highway 21, about 1.5km from the Savannah/Hilton Head International Airport, around 11.30am on Wednesday, authorities said.

The huge plane’s fuselage appeared to have struck the median, and pieces of it were scattered across lanes in both directions. The only part still intact was the tail section, said  spokesman for the Savannah Professional Firefighters Association Chris Hanks.

“It miraculously did not hit any cars, any homes,” Effingham County Sheriff’s spokeswoman Gena Bilbo said. “This is a very busy roadway.”

Motorist Mark Jones told the Savannah Morning News he saw the plane hit the ground in front of him after it appeared to stall.

“I’m still shook up and shaking. My stomach is in knots because I know they’re people just like me. I wasn’t that far from it and I could have just kept going and it would have been me and we wouldn’t be talking right now,” Mr Jones said.

A Puerto Rican official quoted by the Associated Press said nine people were aboard the plane and there were no apparent survivors.

The cause of the crash was not immediately clear, and firefighters were still working to make the crash site safe for investigators, Georgia Air National Guard Senior Master Sergeant Roger Parsons said.

The Air Force said the plane belonged to the 156th Air Wing out of Puerto Rico, and all aboard were Puerto Ricans on a mission to the US mainland.

Local members currently on scene assisting with clean up. pic.twitter.com/lSuRcqTx56

— IAFF574 Savannah (@IAFF574) May 2, 2018

Puerto Rico National Guard spokesman Major Paul Dahlen said initial information indicated there were five to nine people aboard the plane, which was heading to Arizona.

President Donald Trump tweeted that he had been briefed on the crash, sending “thoughts and prayers for the victims, their families and the great men and women of the National Guard.”

The US territory’s Governor Ricardo Rossello expressed his sadness, tweeting that “our prayers are with the families of the Puerto Rican crew”.

-with AAP