A US-Russian space crew, stranded in orbit by the US Columbia tragedy, landed in Kazakhstan on Sunday, but rescuers found them more than two hours later because their capsule missed its landing target.

Mission control said Americans Ken Bowersox and Donald Pettit and Russia's Nikolai Budarin touched down in the Kazakh steppe after almost six months in space.

But mission control held its breath until rescuers scouring the Kazakh steppe in planes and helicopters found them about two hours after the landing.

"Rescue planes have spotted the capsule from the air. The capsule hatch is open," a relieved official at mission control said. "We have radio contact with the crew. Thank God, they are all alive and well."

He added the Soyuz had landed

in a remote spot north of the Aral Sea, some 310 miles short of its target, an unusually large stretch.

It was not clear why the capsule missed its planned landing site, some 55 miles north of Arkalyk in Kazakhstan.

Rescuers quoted by Itar-Tass news agency said they found the crew standing by the capsule waving to them. The crew is due to be taken to the Kazakh capital Astana and later flown to Moscow.

Mission control is usually flooded with applause as crews return safely. Early on Sunday it was silent as experts struggled to understand what was happening.

Experts at mission control said the capsule probably came down in a steeper, so-called ballistic descent, increasing the force of gravity. They added the Soyuz's communication system may have been disrupted by the descent, cutting links with the ground and slowing down rescue efforts.