Three veteran storm chasers were killed while pursuing powerful tornadoes that tore through the US state of Oklahoma, a relative said Sunday.

Tim Samaras, his son Paul and their storm-chasing partner Carl Young died Friday in a twister in El Reno, west of Oklahoma City.

They were the first storm researchers ever killed while chasing tornadoes, media reports said, citing the National Weather Service's Storm Prediction Center in Norman, Oklahoma.

"They all unfortunately passed away but doing what they LOVED," the elder Samaras's brother Jim Samaras said on his Facebook page.

Tony Laubach, a fellow participant in the Tactical Weather Instrumented Sampling in Tornadoes Experiment, or TWISTEX, that Samaras founded, mourned the "devastating loss to the meteorological, research and storm-chasing communities."

Samaras's instruments are said to have offered the first-ever glimpse inside a tornado, and TWISTEX aimed to learn more about the storms in order to help increase the lead time in warnings.

A series of tornadoes battered Oklahoma with high winds, heavy rain and large hail, causing at least 11 fatalities in a state already reeling from a monster twister that claimed two dozen lives last month.

Debris from the chasers' vehicle was strewn about half a mile (0.8 kilometers), Canadian County Undersheriff Chris West told AFP.

Only one of the bodies was recovered from the vehicle. The two others were found about a quarter of a mile in either direction.

Crews hauled away a badly mangled white truck with its windows smashed and its body crushed and twisted almost beyond recognition.

"Tim was a courageous and brilliant scientist who fearlessly pursued tornadoes and lightning in the field in an effort to better understand these phenomena," National Geographic executive vice president Terry Garcia said in a statement.

The Washington-based institution had provided 18 grants to Samaras for his research.

It said he developed his interest in twisters after watching the film "The Wizard of Oz" when he was just six years old. The movie begins with a tornado sweeping heroine Dorothy and her dog Toto away to Munchkinland in Oz.

"Though we sometimes take it for granted, Tim's death is a stark reminder of the risks encountered regularly by the men and women who work for us," Garcia said.

Samaras developed probes to measure the environment inside tornadoes. Researchers had to place the probes in the path of the storm and then escape before being swept away.

He measured the lowest barometric pressure drop ever recorded (100 millibars) at the tornado's center, saying that was equivalent to "stepping into an elevator and hurtling up 1,000 feet (305 meters) in 10 seconds."

Samaras was also known as a star on the Discovery Channel's show "Storm Chasers," which ended last year.

His brother Jim Samaras said the storm chaser "looked at tornadoes not for the spotlight of TV, but for the scientific aspect."

"At the end of the day, he wanted to save lives and he gave the ultimate sacrifice for that," he told The Denver Post.

His final message on the social media site Twitter warned: "Storms now initiating south of Watonga along triple point. Dangerous day ahead for OK--stay weather savvy!"

And despite the big risks the storm chaser often took, Samaras was known to be very cautious and to pay attention to safety.

"He knew where not to be and in this case the tornado took a clear turn toward them," Jim Samaras said.

Weather Channel anchor and meteorologist Mike Bettes had a close call himself in Oklahoma's storms, and described them as highly unpredictable.

The tornado swept up the truck he was traveling in with a crew, throwing it 200 yards (meters) into a field and smashing it to the ground.

"I think this was just an erratic tornado. I think the size of it and the speed of it changed very, very quickly," Bettes told CNN.

Bettes said the frightening experience left him unsure of whether he would ever chase storms again.

In a post on Facebook four days before he died, Tim Samaras wished fellow storm chasers well.

"Everyone enjoy the chase -- and hope that tornadoes wander over open country," he wrote.

"Most of all, I reflect and appreciate the freedom this incredible country has to offer, and the ultimate sacrifices so many have made to make it happen."