The UK has accused Russia of launching a “projectile with the characteristics of a weapon” during a satellite test.
Air Vice Marshal Harvey Smyth, the head of the UK’s space directorate, said the launch "threatens the peaceful use of space" and said the UK is "concerned".
It is the first time the UK has called out Russia for this sort of activity.
The US also condemned the action, describing the event as a test of an anti-satellite weapon.
"Actions of this kind threaten the peaceful use of space and risk causing debris that could pose a threat to satellites and the space systems on which the world depends," AVM Smyth said.
"We call on Russia to avoid any further such testing.
"We also urge Russia to continue to work constructively with the UK and other partners to encourage responsible behaviour in space."
The US Space Command said Russia “injected a new object into orbit” from the satellite Cosmos 2543.
"The Russian satellite system used to conduct this on-orbit weapons test is the same satellite system that we raised concerns about earlier this year, when Russia manoeuvred near a US government satellite," said General Jay Raymond, US Space Force's Chief of Space Operations.
"This is further evidence of Russia’s continuing efforts to develop and test space-based systems, and consistent with the Kremlin’s published military doctrine to employ weapons that hold US and allied space assets at risk."
"What is new here, according to them, is that Russia appears to be testing an actual on-orbit anti-satellite weapon," Dan Wasserbly, Editor of Janes International Defence Review, told Forces News.
"What appears to be like the Russian 'nesting dolls' where the satellite goes up and it's just a satellite and then it releases another satellite and then that satellite itself releases what may be a weapon that could disable or damage an adversary satellite," he added.
Why Is Space Important?
Space is an important factor of military operations, and the need for countries to expand their space capabilities is growing.
Satellites can have encrypted battlefield commands fed through them which help direct military personnel on the ground.
The importance of space has seen the UK announce its first Defence Space Strategy, with RAF Air Command being made responsible for operations.
It is thought space warfare in the future could involve jamming, laser attacks or hacking techniques.