MOSCOW, Russia - Russian cosmonauts onboard the ISS held a flag symbolizing pro-Russian separatists in eastern Ukraine and congratulated Moscow's forces on capturing the region of Lugansk, the space agency in Moscow said Monday.

Roscosmos posted a photograph of cosmonauts Oleg Artemyev, Denis Matveyev and Sergei Korsakov holding the flag of the self-proclaimed separatist Lugansk People's Republic in space.

"We celebrate on earth and in space," the space agency said on Telegram.

Watch more News on iWantTFC

Russia on Sunday proclaimed it now controls the entire Lugansk region in eastern Ukraine, after capturing the key city of Lysychansk following weeks of bloody battles.

• Pro-Russia rebels claim to 'encircle' key Ukraine city

Roscosmos said the cosmonauts "join in on the congratulations" to the head of the separatist statelet, Leonid Pasechnik.

The Russian space agency has been hit by Western sanctions since President Vladimir Putin sent troops to Ukraine in February.

• Russian space agency wants foreign partners to pay it in rubles
• NASA insists space station unaffected by Russian war

The ISS, a collaboration among the US, Canada, Japan, the European Space Agency and Russia, is split into two sections: the US Orbital Segment, and the Russian Orbital Segment.

bur/jm

© Agence France-Presse