Michael Foale (l) and Alexander Kaleri (r) form the Expedition 8 crew

Both crew members had been on a spacewalk when problems were detected in one of their protective suits.

Plans for Russian Alexander Kaleri and UK-born Michael Foale to stay out for several hours were cut short.

Mission controllers in Houston and Moscow had been keeping watch as the station had been left empty for the first time in five years.

Nasa admitted it had at first been sceptical of Russian plans to send the spacemen outside the platform together.

'Strangely warm'

But it decided the work planned for the walk needed to be carried out prior to the arrival of the next crew in April. Nasa said the work was not critical but would have to be done eventually.

British-born Mr Foale, who went to school in Canterbury, in Kent, and Mr Kaleri opened the station's hatches at 2117 GMT, according to Russian mission control.

The US commander and the Russian flight engineer were three hours into their mission to conduct experiments and carry out routine maintenance when the temperature control problem with Mr Kaleri's suit was identified.

"It's strangely warm," Mr Kaleri told controllers.

List of jobs

Both men returned safely to the Russian Zvezda module, after about half the planned time outside.

The usual routine on the ISS is for two crew members to go spacewalking at the same time, acting as "buddies" to check on each other's safety. At least one other astronaut, either on the station or viewing from the US space shuttle, would normally keep an eye on them.

But with the shuttles grounded following the Columbia disaster and ISS crews reduced to just two individuals, this practice is simply not possible at the moment.

The list of jobs that need doing on the ISS to keep it in good order is lengthening, and the station's next two-man crew - Expedition 9 - expects to make two spacewalks, conducting far more critical work.

Commander Foale had said he was happy to carry out the five-and-a-half-hour walk, recalling that pairs of Apollo astronauts had made lengthy walks across the Moon's surface in the 1960s and 1970s without anyone staying behind on their lander.