SpaceX's Falcon 9 rocket has exploded after liftoff in a mission that was bound for the International Space Station.

Sunday morning's launch from Cape Canaveral, Florida, initially appeared to go as planned under clear skies.

But seconds after takeoff, NASA confirmed the mission had ended in failure as the 208ft (63 metre) rocket disintegrated.

A live webcast went silent about two minutes and 19 seconds into the flight, and debris could be seen showering into the Atlantic Ocean.

NASA commentator George Diller said: "The vehicle has broken up.

"At this point it is not clear to the launch team exactly what happened."

He noted an "anomaly" had occurred after the rocket ignited its nine Merlin engines and reached supersonic speed.

The spacecraft was carrying more than 5,200lb (2,360kg) of gear, including food, supplies and science experiments.

"This was a blow to us. We lost a lot of research equipment on this flight," NASA Associate Administrator Bill Gerstenmaier told a news conference.

The disaster was the first of its kind for privately owned Space Exploration Technologies, led by entrepreneur Elon Musk.

He said an over pressurisation occurred in the liquid-oxygen tank of the rocket's upper stage.

"That's all we can say with confidence right now," Musk said via Twitter.

The mishap occurred on the 44th birthday of the tycoon, who also runs electric car company Tesla.

The Falcon 9 rocket has previously made 18 successful launches since its 2010 debut, including six cargo runs for NASA.

But it was the California company's third failed attempt this year to land a reusable rocket booster back on its platform barge in the ocean after liftoff.

SpaceX has the goal of one day making rockets as reusable as airplanes.

This is also the third failed station shipment in eight months.

An Antares rocket, built by SpaceX rival Orbital ATK, blew up on the launch pad in Virginia in October.

In May, a Russian Progress rocket spun out of control, unable to reach the space station.

There are several men currently living at the orbital hub, including US astronaut Scott Kelly and two Russian cosmonauts, Mikhail Kornienko and station commander Gennady Padalka.

"Sadly failed," Kelly said via Twitter. "Space is hard."

The crew has about four months of food and supplies on board, so the accident doesn't pose an immediate problem.

Russia expects to launch supplies to the space station on Friday from Kazakhstan.

The Dragon cargo capsule launched on Sunday was bringing a large parking space, known as an International Docking Adaptor, designed to make it easier for other commercial spacecraft to dock at the orbiting lab in future.

Also on board were dozens of science experiments, including one that would have allowed astronauts to grow their own cabbage and lettuce.

Another experiment by school students aimed to study how worms behave in a compost pile in space.