He is only 14 but already knows how to assemble a Kalashnikov rifle. Denis is a child soldier in the making - eager to join the pro-Russian militants fighting Ukrainian troops.
"If I were an adult, I would fight," the skinny boy with a dishevelled crew-cut said in a war-scarred town deep in the heart of the rebel-run east of the ex-Soviet state.
"I want to see war, to learn how to shoot, to see the tanks," he said with an air of excitement as two adult rebels stood nodding at his side.
The UN children's agency said in January it had no proof of minors being used in one of Europe's bloodiest and most diplomatically-charged conflicts since the end of the Cold War.
UNICEF believes that about 250,000 children are being exploited in wars fought across nearly two dozen countries - many of them in Africa.
But the Western-backed leaders in Kiev accuse the rebels of training a small army of child soldiers in schools under their control.
About 20 kids between the ages of 14 and 19 are still taking training lessons in the town of Khartsyzk - home to 60,000 people prior to the breakout of hostilities and a flood of migrants for safer regions that followed -- in the first weeks of their summer break.
Some like Denis are learning basic drills. But his parents are understandably wary after being trapped in fighting that has killed 6,500 and shows few signs of abating 15 months on.
"They do not talk about the war with me. They hate it," Denis said. "They do not even watch the news."
Others like 17-year-old Alina are taking first aid lessons provided by the rebel command.
"We are still children and not ready to go to the front," she conceded.
"But if something were to happen, I would be able to help out."
'Back to the USSR'
The Khartsyzk military lessons for children are organised by Patriotic Donbass - the local name for a rustbelt region that hugs the 2,000-kilometre (1,250-mile) Don River and includes the self-declared "people's republics" of Lugansk and Donetsk.
Patriotic Donbass boss Yury Tsupka - a 53-year-old who disdains the Ukrainian nationalists who fight as volunteers across the war zone - said he only wanted to reinstate the old Soviet tradition of teaching army skills in school.
"We decided to go back to what we had in the USSR," the fatigues-clad Tsupka said.
"We will also teach them to dig trenches, to work the terrain."
Tsupka said more and more schools across the heavily Russified region were running such military clubs. He said there were at least four others in surrounding towns alone.
But not all of them are providing simple training.
Some have seen their pupils actually join the Khartsyzk separatist units stationed in the mine-strewn fields that stretch 20 kilometres (12 miles) east of the rebel stronghold city of Donetsk.
'Not afraid of blood'
Anya and Katya are genial twins who are used to wearing heavy combat boots.
They seem at ease and not the slightest bit regretful recalling how - at the tender age of 19 - they made the life-altering decision to quit their technical college and join one of the local militia forces.
"We studied and lived in Donetsk when the war started," Katya said.
"We decided to join the rebellion when we learned that kids were being killed."
Monitors from the Organization for Security and Co-operation in Europe (OSCE) believe that at least 68 children have died and 180 have been wounded since fighting began in March 2014.
The campaign's brutality has splintered family allegiances and left psychological scars on both ethnic Russian and Ukrainians - fellow Slavs who had lived in relative harmony even after the Soviet Union broke up.
Anya admits that "at first, mom would not let us" join the war.
But she then she caved, and started going along with her daughters to treat rebels wounded at the front.
"Before the war, I used to be afraid of blood - of its smell," Katya said. "I am not afraid of blood any more."