From patriotic songs blaring on the metro to parties on the International Space Station, Russia proudly celebrated on Tuesday 50 years since rocketing Yuri Gagarin into the first human orbit.

In a video link with space, Russian President Dmitry Medvedev told astronauts aboard the orbital station that space exploration remained Russia's "priority".

"In those 50 years, we absolutely can't imagine life without space, without your flights," Medvedev told the crew from Russia's Mission Control Centre, named after the legendary father of the Soviet space programme Sergei Korolyov.

"Space is our priority."

Space station Commander Dmitry Kondratyev said his current six-person US, Russian and European crew would celebrate the holiday from the "front lines" in weightlessness.

"This flight stirred the whole world and showed what humanity was capable of," said veteran Soviet cosmonaut Alexei Leonov, 76, who completed the first space walk in 1965.

"He invited us all into space," Leonov told at Kremlin hall filled with some of the world's most well-loved space icons, citing a tribute from the first man on the moon, US astronaut Neil Armstrong, to Gagarin.

Since Gagarin's epic journey into the unknown 50 years ago, some 500 people have followed him into space.

"If Yuri Gagarin had not made this flight I would not have flown to the moon," said US astronaut Thomas Stafford, commander on the first US lunar landing in 1969.