A Russian Soyuz spacecraft has returned to Earth, but came down more than 400km (250 miles) away from its planned touchdown point, say Russian officials.

The crew are safe, but were subjected to severe G-forces during re-entry, said a spokesman for mission control.

He said they were examined at the landing site by medical staff.

On board were Yi So-yeon, South Korea's first astronaut, Yuri Malenchenko from Russia and American Peggy Whitson, who broke Nasa's record for time in space.

The Russian capsule was returning from a mission to the International Space Station.

It touched down some 420km away from its planned landing point in the Kazakh steppe, and some 20 minutes later than schedule.

"The main thing is that the crew is alive and healthy," said Anatoly Perminov, head of the Russian federal space agency.

They underwent medical examinations after landing, having been subjected to high G-forces in the descent.

Mr Perminov said the craft followed the back-up landing plan, a so-called "ballistic re-entry" - a plunge with an uncontrollable, steep trajectory.

He said the crew missed the target because they changed their landing plan at the last minute without telling mission control.

In October, a crew returning from the International Space Station had a similar experience, touching down in Kazakhstan 200km (120 miles) from its intended landing site, in temperatures of 6C ( 43F).

Ms Yi had spent 11 days conducting tests at the space station.

Yi So-yeon, South Korea's first astronaut after landing 19 April 2008
South Korea's Yi So-yeon spent 11 days at the International Space Station

South Korea, which paid Russia $20m (£10m) for her trip into space, is investing heavily in space technology and is due to launch its first rocket later this year.

Ms Whitson now holds the record for the cumulative length of time spent in space by an American at 377 days, the US space agency Nasa said earlier.

This was Yuri Malenchenko's third long-duration spaceflight. He spent 126 days aboard space station Mir in 1994, and 185 days on the ISS in 2006.

He also flew on a 12-day shuttle mission in 2000. He has accumulated 515 days in space during his four flights. This is the ninth highest total of cumulative time.