The International Space Station's crew has doubled after a Russian capsule carrying three astronauts docked at the orbiting outpost.
The Soyuz TMA-15 capsule carrying the astronauts docked with the ISS at 1334 BST (0834 EDT).
The new crew members will spend a total of six months aboard the station, raising its crew complement to six for the first time.
The astronauts opened the hatch at 1514 BST (1014 EDT).
The current space station commander Gennady Padalka had to tug hard on the hatch before it opened, allowing Canadian Robert Thirsk through to greet him.
Roman Romanenko, from Russia, Frank De Winne, from Belgium, and Canadian astronaut Mr Thirsk blasted off from Baikonur Cosmodrome in Kazakhstan on Wednesday morning.
The current crew, consisting of Russian cosmonaut Mr Padalka, Nasa astronaut Michael Barratt and Japanese astronaut Koichi Wakata, will not come straight home.
All five partner space agencies are now represented on the ISS
Instead, they will stay aboard the station until a new crew rotation in October.
Simonetta di Pippo, the European Space Agency's director of human spaceflight, said: "We thank the three astronauts for their hard work."
She added that it took "thousands of people around the world to reach this achievement. It's an international achievement".
A primary objective of the mission will be to assess how well the six crew members live together in the confines of the space station.
After four months, Mr De Winne will take over as commander of the ISS from Mr Padalka.
This will mark the first time a European Space Agency astronaut has taken charge of a crew in orbit.
The mission will also be the first occasion that all five ISS partner agencies are represented by crew members on the orbiting outpost.
Nasa has also signed a deal with the Russian Space Agency worth $306m for crew transportation in 2012 and 2013.
The agreement covers four launches aboard the three-person Soyuz capsules to rotate crews in the orbiting laboratory.
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