Astronauts on the International Space Station (ISS) were ordered to shelter in an attached spacecraft after the structure suddenly started leaking more air.

Five of the seven crew were directed to go into the docked SpaceX shuttle Dragon "Freedom" on Friday afternoon and were braced for a potential evacuation.

Meanwhile, two remaining personnel - a pair of Russian cosmonauts - attempted to repair a part of the Russian segment of the ISS, where the leaks had started increasing on Monday.

The repairs were paused and the crew ordered back onto the ISS by Nasa on Friday afternoon.

Jessica Meir, Jack Hathaway, Sophie Adenot and Andrey Fedyaev, who arrived on the ISS in February, had been sheltering on the docked ship, along with another astronaut Chris Williams.

They had been told to put on their spacesuits so they were ready to undock and return to Earth at short notice.

The Dragon effectively functions as a lifeboat - attached to the station but ready to detach the moment the order is given.

The trigger for the order was a worsening air leak in the transfer tunnel, known as PrK, leading to a section of the Russian segment of the station called the Zvezda service module.

Russian cosmonauts, station commander Sergey Kud-Sverchkov and flight engineer Sergei Mikaev, attempted to fix the problem. Their escape route was the separately docked Soyuz MS-28 spacecraft.

It is not the first time the station has had to deal with this problem - the cracks responsible have persisted on and off for around six years.

However, following the arrival of a Russian cargo ship last month, the Russian space agency Roscosmos noticed a fresh slow pressure drop in the tunnel, prompting the decision to move beyond patchwork fixes and attempt a more extensive repair operation on Friday.

But it was the method they were planning to use that prompted the order to take shelter, according to news agency Reuters.

Kud-Sverchkov and Mikayev were said to be using a saw to try and get into an area to access the crack that was leaking air.

Nasa disagreed with the method they were using and mission control in Houston ordered five crew to take "safe-haven" procedures on the Dragon ship.

When Roscosmos told their crew to pause repairs, Nasa instructed the astronauts to return to the station.

Nasa spokeswoman Bethany Stevens said on X: "Given this development, Nasa has instructed the crew members inside the Dragon spacecraft to end the safe haven procedures and return to planned operations aboard the International Space Station."

Russian news agency Tass, citing Roscosmos, reported that nothing had been threatening the safety of the crew or the ISS's onboard systems.

The ISS, which spans the length of a football field, is the largest human-made object in space.

It has been continuously operated by a US-Russian-led consortium that includes Canada, Japan and 11 European countries since 1998.