Russian cosmonauts on board the ISS held a flag symbolizing pro-Russian separatists in eastern Ukraine and congratulated Moscow's forces on capturing the region of Luhansk, 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 Luhansk People's Republic in space.
"We celebrate on earth and in space," the space agency said on Telegram.
Russia on Sunday proclaimed it now controls the entire Luhansk region in eastern Ukraine after capturing the key city of Lysychansk following weeks of bloody battles.
Roscosmos said the cosmonauts "join in on the congratulations" to the head of the separatist state, Leonid Pasechnik.
The Russian space agency has been hit by Western sanctions since President Vladimir Putin sent troops to Ukraine in February.
The ISS, a collaboration among the U.S., Canada, Japan, the European Space Agency and Russia, is split into two sections: the U.S. Orbital Segment and the Russian Orbital Segment.