The US shuttle Discovery undocked from the International Space Station (ISS) on Wednesday to begin its return journey to Earth, NASA said.

After an eight-day stay, Discovery detached from its bay at the orbiting laboratory on schedule at 1953 GMT, as they passed 217 miles (350 kilometres) above the Indian Ocean.

"Houston, we have a physical separation," said a member of the shuttle crew, according to a broadcast of the manoeuvre on NASA TV.

The shuttle and its crew of seven astronauts are on course to return to Florida's Kennedy Space Center at 1.43 pm on Saturday, if weather conditions at the base remain favourable.

Before leaving behind the ISS, the shuttle crew were to move their craft 200 metres (yards) away to take photos and record film of the orbiting outpost.

Discovery docked at the ISS on 17 March, two days after its launch. One of the mission's biggest tasks was to deliver the last set of solar arrays, which were successfully unfurled on Friday.

The ISS now has four solar panels, two per wing, containing 32 800 cells that convert sunlight into electricity.

They will boost the outpost's full power generation from 90 to 120 kilowatts, providing the power the space station needs to carry out scientific experiments aboard Kibo and the European Columbus laboratory.

AFP