LOS ANGELES (AFP) - A factory worker who killed three people and wounded 17 in a shooting spree in Kansas had just been served with a restraining order, authorities said on Friday, in a possible trigger for the deadly rampage.

The latest mass shooting to rock the United States unfolded on Thursday at a lawn mower plant in a town north of Wichita, and ended when police shot dead the gunman identified as Cedric Larry Keith Ford, 38.

President Barack Obama telephoned the mayor of Hesston, David Kauffman, to offer condolences for the shooting, coming less than a week after an Uber driver in Kalamazoo, Michigan shot dead six people seemingly at random.

"These are two more communities in America that are torn apart by grief," Obama said during a speech in Jacksonville, Florida. "We cannot become numb to this."

As he has done after each mass shooting of recent times, Obama renewed his call for action to stem the epidemic of gun violence, while urging national media to open a serious debate on gun control.

"Once a week we have these shootings, and it doesn't dominate the news, and that has got to change," he said.

Ford, an employee at the Excel Industries plant, was served a "protection from abuse" order at his workplace about 90 minutes before the rampage began, Harvey County Sheriff T. Walton told a news conference.

Soon after receiving the order at 3.30pm, he left the factory in Hesston, a tight-knit community north of Wichita.

Walton said Ford was upset by the order but didn't display any "outrageous" behaviour at the time.

The first shooting was reported an hour and a half later, as Ford opened fire from his car on a man driving past with his two children, hitting him in the shoulder.

"He was randomly shooting people," said Walton.

Armed with an assault rifle and a pistol, Ford took aim at a second approaching car, but the female driver wasn't hit. "A miracle. It just missed her. Went through the windshield," Walton said.

Ford then drove an oncoming vehicle off the road, shot the driver, and used the stolen car to return to Excel, where he shot a woman in the parking lot and fired at a sheriff's deputy who escaped unhurt.

Ford entered the building and opened fire, injuring 14 more people and killing three.

A police officer then confronted him and shot him dead.

"Currently we have 14 people in various hospitals," Walton said. "Those conditions range from stable to critical, and one going into surgery as we speak."

Walton said 200 to 300 people were inside the building at the time, and said many more would have died had Ford not been shot.

The sheriff confirmed that Ford had a criminal history, and that it was not known how he had been able to obtain the weapons used in the shooting.

"All I can say is, he's been in my jail a couple of times before," Walton said.

"We're conducting traces of the weapons themselves. We're also doing an investigation of how he got those weapons."

According to media reports, Ford had recently moved to the area from Miami, and had an extensive criminal record including a history of prowling, loitering and illegal weapons possession. Walton did not discuss those reports.

The sheriff said that "protection from abuse" restraining orders are usually made "because you're in a relationship where there's been some kind of violent occurrence."

He did not name the other person concerned by the order, but said they did not work at the plant.

Local media identified Ford as a factory painter who had posted a picture of himself on Facebook with an assault rifle.

Matt Jarrell, also an Excel painter, told CNN affiliate KSNW that "never in a million years" would he have expected Ford to do something of the kind.

"He was a mellow guy," Jarrell said. "He was somebody I could talk to about anything."

Walton said police surrounded the gunman's mobile home in nearby Newton after the shooting but that his roommate refused to allow them in, resulting in a standoff.

Officers later obtained a warrant and entered the home to find it empty.

Such attacks have become tragically commonplace in the United States, where gun violence is responsible for some 30,000 deaths per year and 330 mass shooting incidents were recorded last year.