A doctor who was playing golf when Harrison Ford crashed into the course says he feared the actor's plane would burst into flames.

"He was obviously moaning and in pain," spinal surgeon Sanjay Khurana said.

"My task, if you will, was to get him out of the airplane in a somewhat urgent manner because the fuel was leaking."

The 72-year-old was flying solo in a World War Two training aircraft when it crashed into Penmar golf course in the Venice area on Thursday afternoon.

Dr Khurana told ABC news: "He's obviously an iconic individual and when he lay there as I was trying to check his airway, his blood pressure, it was obvious by his face it was Harrison Ford."

The plane remained at the crash site on Friday morning as federal aviation investigators tried to determine what made it come down.

In audio with air traffic control, Ford, who was flying at 3,000 feet, can be heard saying in an urgent voice: "Engine failure," before requesting "immediate return" to the airport.

The single-engine plane clipped a tree as it went down shortly after taking off from Santa Monica Airport, about a mile away, the LA Fire Department said.

The yellow plane with stars on its wings was upright and mostly intact after the crash. No one on the ground was hurt.

Witnesses were reported by local media as saying the actor was helped out of the plane by several bystanders and that he could use his legs.

Ford's son Ben, who is at his father's bedside in hospital, tweeted: "At the hospital. Dad is OK. Battered but OK!

"He is every bit the man you would think he is. He is an incredibly strong man."

Ford's publicist Ina Treciokas said: "He was banged up and is in the hospital receiving medical care. The injuries sustained are not life-threatening and he is expected to make a full recovery."

Ford appeared to have used his extensive piloting experience to skillfully bring down the plane on the golf course and avoid nearby homes.

Christian Fry, of the Santa Monica Airport Association, said: "I would say that this is an absolutely beautifully executed - what we would call - a forced or emergency landing, by an unbelievably well-trained pilot."

LA Police Department spokeswoman Officer Nuria Vanegas said the cause of accident appeared to be "mechanical failure".

Carlos Lugo, 63, who was playing golf on the green, said he saw the plane lose power and turn around in an apparent attempt to return to the runway at Santa Monica Airport.

"When he flew over us we knew it was too late to make it back to the airport," he said.

Best known for his roles in the blockbuster films Star Wars and Raiders Of The Lost Ark, Ford is an experienced aviation enthusiast and has been the owner of several planes.

He took his first flying lessons in college, gave up due to lack of money, but got back into it after becoming an established film star.

The Ryan Aeronautical plane that he was flying was built in 1942 - the year Ford was born - and registered to the company MG Aviation Inc.