SpaceX rocket explodes at launch site in Florida

An unmanned SpaceX Falcon 9 rocket has exploded on the launch pad at Cape Canaveral in Florida during a test, destroying it and its payload, but there were no injuries, the private space firm said.

It is believed to have destroyed a $260 million satellite owned by Facebook that was intended to be the social media giant's first launch into delivering internet to the developing world.

A dense plume of black smoke filled the air following the blast. The US space agency NASA said the incident took place shortly after 9:00 am (11pm AEST).

"SpaceX can confirm that in preparation for today's static fire, there was an anomaly on the pad resulting in the loss of the vehicle and its payload," the company said. "Per standard procedure, the pad was clear and there were no injuries."

Brevard County Emergency Management said there was no threat to the public from the incident.

SpaceX, which is based in California, is headed by internet entrepreneur Elon Musk, who wants to revolutionize the launch industry by making rocket components reusable.

The company had successfully launched a Falcon 9 last month, sending a Japanese communications satellite into orbit and then landing the rocket on a floating drone ship.