In a sandy ravine outside Kyiv, a group of soldiers in camouflage were learning the basics of warfare -- in Russian.
A newly-formed battalion within the Ukrainian army is made up of some 50 Russians who have come to fight against their fellow citizens.
"I took the decision to get into Ukraine as soon as possible to fight against Russia, against the Putin regime, against imperialism," said one fighter, who goes by the call sign "Grecha" (Buckwheat).
The war in Ukraine has attracted a motley bunch of foreign volunteers, most of whom serve in the army's International Legion, which also incorporates the Siberian Battalion.
Fighters covered their faces and did not want to give their names.
They were a varied group -- both ethnic Russians with long-standing opposition views and members of Siberia's minority ethnic groups.
This is not the only Russian unit fighting for Ukraine.
This spring, two others came into the spotlight after brief incursions across the Russian border: the Russian Volunteer Corps, which has links to the far-right and football hooligans, and another unit called the Freedom of Russia Legion.
The International Legion's spokesman said he could not give details about how the Russians enter Ukraine but said some come in small groups, others alone.
"We don't bring them over in car boots," he stressed.
"It's not illegal crossings. It's all absolutely legal. We need to look for various loopholes within international and Ukrainian legislation so they can get into Ukraine."
None are prisoners-of-war, he said, and they are on military contracts.
"Grecha" said he was born in Ukraine's Crimea but had lived in Moscow, working as a paramedic.
"We need to free Ukraine, the motherland where I was born in Crimea, that's my dream," he said.
He said his political views are not clearly defined but they are "more liberal than in Russia now".
Grecha added that he had joined opposition protests against the war but felt they were "pointless".
"In Russia at the moment there is a dictatorship which of course I am extremely unhappy about, because it might not concretely affect me right now: I'm not in jail, I'm not a foreign agent but I feel the state gives less and less freedom to its citizens," the fighter said.
"Sooner or later it will be one big concentration camp, basically it already is."
He left Russia last year and sought to enter Ukraine, but "at first there was no organisation, there was no information about how to get in."
He spent time in countries that are visa-free for Russians, living mainly in a tent.
He said he eventually found an organisation called the Civic Council, which says on its website that it recruits for the Siberian Battalion. Its Facebook page says it is in Warsaw.
Grecha said the organisation agreed his transit along with his wife.
"I spent some time waiting in third countries and at one wonderful moment they wrote to me that we can go out, they provided the route and that way we got into Ukraine."
He admitted he had not told his parents he was joining up.
"They have different views on this war. We've talked about this topic many times and argued many times."
Another fighter -- "Shved" (Swede) -- said he had left Russia more than a decade ago "because of political persecution" and had lived in Sweden since 2011.
"I had taken part in anti-government, anti-Putin activities for a long time and was forced to emigrate," he said, calling himself "an anarchist" and partially concealing his face.
Prominent Russians known to have joined the Siberian Battalion include Alexei Makarov, a former member of the National Bolshevik Party who was granted refuge in Sweden, and anti-Kremlin activist Ildar Dadin.
"In this war, Ukraine stands on the side of people's freedom," Shved said, adding that he began fighting last summer with another unit.
"I see what needs to be done now is to achieve the defeat of Putin's Russia," he said, hopeful that this would spark political change in Russia and Belarus.
"And for that we need Ukraine's victory."
