An unmanned SpaceX Falcon 9 rocket exploded on the launch pad during a test in Florida, destroying a satellite that Facebook planned to use to beam high-speed internet to Africa.
The blast at Cape Canaveral on Thursday -- though it caused no injuries -- marks a setback for the California-based private space firm and its founder, internet entrepreneur Elon Musk, who wants to revolutionize the launch industry by making rocket components reusable.
"Loss of Falcon vehicle today during propellant fill operation," Musk tweeted. "Originated around upper stage oxygen tank. Cause still unknown. More soon."
Dramatic footage broadcast by ABC News showed the rocket burst into a roaring ball of flame amid what appeared to be a succession of blasts -- sending its payload tumbling to the ground as a dense plume of black smoke filled the air.
"At approximately 9:07 am ET (1307 GMT), during a standard pre-launch static fire test for the Amos-6 mission, there was an anomaly at SpaceX's Cape Canaveral Space Launch Complex 40 resulting in loss of the vehicle," the firm said.
"Per standard operating procedure, the pad was clear and there were no injuries."
But the explosion destroyed the Israeli communications satellite that the Falcon 9 was due to deliver into orbit on Saturday -- drawing a dismayed reaction from Facebook chief Mark Zuckerberg.
"As I'm here in Africa, I'm deeply disappointed to hear that SpaceX's launch failure destroyed our satellite that would have provided connectivity to so many entrepreneurs and everyone else across the continent," Zuckerberg said on his Facebook page.
Facebook was contracted to use the Amos-6 to provide broadband internet coverage for large parts of sub-Saharan Africa and other remote parts of the world as part of the social media giant's Internet.org initiative.
"Fortunately, we have developed other technologies like Aquila that will connect people as well," Zuckerberg said, referring to the solar-powered plane being developed by Facebook to make the internet available in remote areas.
"We will keep working until everyone has the opportunities this satellite would have provided."
European satellite operator Eutelsat -- Facebook's partner in the project -- said in a statement it was committed to expanding broadband access in Africa despite the loss of the Amos-6.