An unmanned NASA rocket has exploded seconds after lift-off from a commercial launch pad in the US state of Virginia.

The Antares rocket launched on Tuesday was on a mission to supply the International Space Station when it exploded and crashed back to earth, a NASA TV broadcast showed.

The 14-storey rocket, built and launched by Orbital Sciences Corp, bolted off its seaside launch pad at the Wallops Flight Facility. It exploded seconds later.

The cause of the accident was not immediately known, said NASA mission commentator Dan Huot. 

NASA said there were no injuries. 

"This has been a lot of hard work to get to this point," Orbital Sciences Executive Vice President Frank Culbertson told the launch team just before lift-off. 

The Launch had been delayed one day after a boat sailed into a restricted safety zone beneath the rocket's intended flight path. 

Virginia-based Orbital Sciences is one of two companies hired by NASA to fly cargo to the station after the space shuttles were retired. Tuesday's planned flight was to be the third of eight under the company's $1.9bn contract with NASA. 

Antares carried a Cygnus spacecraft packed with 5,055 pounds (2,293kg) of supplies, science experiments and equipment, a 15 percent increase over previous missions. 

Cygnus was to loiter in orbit until November 2, then fly itself to the station so astronauts can use a robotic crane to snare the capsule and attach it to a berthing port. The station, a $100bn research laboratory owned and operated by 15 nations, flies about 260 miles (418km) above Earth.

Source: Agencies