Some are wounded, most are very young and all want to go home. President Volodymyr Zelensky calls Russian soldiers captured in the lightning offensive into the Kursk region, Ukraine's "exchange fund".
He hopes the prisoners of war taken in the surprise push that caught Russia off guard can be quickly exchanged for some of the 6,500 or so Ukrainian soldiers that Moscow says it holds.
"This operation has become our largest investment in the process of releasing Ukrainians from Russian captivity," Zelensky said last week.
"We have already captured the largest number of Russian prisoners in one operation."
Ukraine has said large numbers of Russian servicemen -- reportedly in the hundreds -- gave themselves up during the offensive that began on August 6.
AFP asked for access to some of the POWs being held just across the border in Ukraine's Sumy region.
Though Ukrainian guards were standing nearby, the prisoners did not appear to be talking under duress.
One 22-year-old Russian POW -- a conscript -- said he and others were "simply abandoned by our command" when Ukrainian troops appeared.
"Everything was normal, everything was fine. And then this unexpected moment turned everything upside down," he said, sitting on a bunk in his cell.
"It was unexpected," he repeated.
The young man, who wore checked trousers and plastic slippers, said his hope was "to be exchanged and go back home -- back home to my family".
Another detainee, a 42-year-old border guard with a bandaged leg, said he was captured on the first day of the offensive.
"There was a complete encirclement and there were no opportunities to break through. So the decision was made to surrender," he said.
"I hope that they will exchange me and I will return home. My biggest hope is that, of course," he said.
The Ukrainian offensive caught Russia off guard.
Kyiv said thousands of its troops took part in the incursion, which comes two and a half years after the start of Russia's invasion of Ukraine.
The deputy head of the facility told AFP that "very large numbers" of Russian POWs have been captured so far, without giving a precise figure.
The POWs had initially been "afraid of everything", he said, but "came to life" after a couple of days when they saw that they were being well treated.
"On the battlefield they are hated soldiers and when they are captured they become ordinary people," said the guard, who gave his name as Volodymyr.
Ukrainian officials have not given a precise number of prisoners of war captured but have said many were young conscripts captured in the chaotic first days of the incursion.
Officials say 3,000 Ukrainian soldiers have been repatriated since the start of the war but "thousands" are still in Russian captivity.
At a meeting with foreign media including AFP in June, Russian President Vladimir Putin said Russia had 6,465 Ukrainian soldiers while Ukraine had 1,348 Russian soldiers.
There are regular exchanges between the two sides but usually involving only a few dozen people.
This time, Ukraine has said it is already in talks with Russia over an exchange for the Kursk POWs.
Human rights ombudsman Dmytro Lubinets said last week he had been contacted by his Russian counterpart Tatyana Moskalkova, claiming this was the first time that Moscow had initiated contact for a prisoner swap.
"I see that this situation... has at least forced the Russian side to take the initiative," he said.
