Three astronauts landed safely in the Kazakh steppe aboard a Russian Soyuz capsule on Tuesday after a stay of over five months aboard the International Space Station, Russian mission control said.

American Mike Fossum, Japan's Satoshi Furukawa and Russia's Sergei Volkov touched down outside the remote settlement of Arkalyk in Kazakhstan just before sunrise after undocking from the ISS earlier in the day.

"It has landed," said a message flashed on the screen at Moscow mission control shown in a live relay. State television pictures showed the astronauts extracted from the capsule apparently in good health.

The Soyuz capsule landed on its side rather than its bottom after its descent to Earth with a parachute, mission control said, adding that this was not unusual. The landing was on time and on target at 0226 GMT.

The hitch-free landing of the Soyuz is a boost for the Russian space programme, which has been battling to restore confidence in its reliability after a spate of disasters in unmanned spaceflight.

State television pictures showed ground workers moving quickly to carry the three men from the capsule to protect them from the initial shock of temperatures of minus 15 degrees Celsius after their half year stay on the ISS.

Volkov was the first to emerge, followed by Fossum and Furukawa. All were carried out by ground workers as the experience of prolonged weightlessness means that they cannot initially walk unassisted.

The three men were sat down in chairs, swathed in blue rugs and blankets to protect them from the sub zero morning temperatures as dawn broke over the snow-dusted steppe. Fossum was shown chatting on a mobile phone.

They were then lifted -- still in their chairs -- to a nearby medical tent put up next to the touchdown site to have their space suits removed and go through standard medical tests.

The three were then helicoptered to the northern Kazakh city of Kostanay for a farewell ceremony where they were wore traditional Kazakh hats and were presented with matryoshka dolls.

After almost half a year in each other's company they were to split up, with Fossum and Furukawa returning to the United States and Volkov flying to Moscow.

It was during their stay on the ISS that a Russian unmanned Progress supply ship carrying supplies for the station crashed into Siberia in August shortly after launch, forcing a complete rejig of the timetable for manned spaceflight.

This capped a disastrous year for the Russian space agency which also saw the loss of three navigation satellites, an advanced military satellite and a telecommunications satellite due to faulty launches.

Hours after the landing, the Russian space agency publicly acknowledged for the first time that its Phobos-Grunt probe for Mars's largest moon, launched on November 9, was also likely lost.

The probe has failed to head out of Earth's orbit on its course to the red planet and its moon Phobos.

"There is little chance that we will be able to realise this mission," the deputy head of Roscosmos Vitaly Davydov said at mission control, quoted by Russian news agencies.

The three returned astronauts had spent 167 days in space -- slightly more than the 161 day mission originally envisaged as the return was delayed by almost a week due to the Progress mishap.

Their return to Earth leaves three astronauts behind on the ISS, American Dan Burbank and Russians Anton Shkaplerov and Anatoly Ivanishin who blasted off from Russia's Baikonur cosmodrome in Kazakhstan on November 14.

They will be joined by another multinational crew of three that is due to take off from Baikonur on December 21.

Following the retirement of the US shuttle in July, Russia is currently the only nation capable of transporting humans to the ISS.

Unlike the horizontal landing shuttle, the Soyuz returns to Earth vertically with a parachute in a procedure whose basic principle has changed little in the last decades but is admired worldwide for its simplicity and reliability.