Names marked with an asterisk have been changed to protect identities.
In February, Kharkiv Polytechnic graduate Dmitry* was visiting Mariupol from the United Kingdom to refurbish his recently purchased apartment.
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But soon, Moscow invaded Ukraine.
He says he was rounded up by Russian soldiers during the siege of the port city and later sent through four “filtration camps” in Russia-occupied Ukrainian territory.
Moscow has said it protects Ukrainians by providing them refuge as the war intensifies, and has referred to “checkpoints for civilians leaving the zone of active hostilities”.
But Kyiv claims what the Kremlin calls evacuations are really forced deportations carried out with questionable motives.
And Washington alleges that “filtration” efforts are designed to single out Ukrainians who are considered threats to Russia’s offensive.
In the end, Dmitry never got to live in his newly renovated flat.
His property, where he had important documents, some belongings and money, was destroyed amid shelling.
The 25-year-old is now seeking shelter in Luxembourg.
Speaking to Al Jazeera from his hostel there, he said he still wakes up in sweats, traumatised by his experiences in the camps.
From March to April, he said he faced death threats and relentless questioning by Moscow-backed officials at camps in the towns of Staryi Krym, Dokuchaevsk, Taganrog and Novoazovsk, which are near the Russian-Ukrainian border.
He said Russian authorities frequently taunted him and he saw other prisoners beaten, tortured and left unconscious.
In the first camp, in Staryi Krym, Dmitry said he was held for a day in a building with cracked glass windows.
“It was very cold, I slept on a chair. They kept us without food, water and information about our loved ones,” he said.
“I had to listen to their sick minds. I was depressed that I could not answer them because it could end badly for me and my family.”
“[They forced me to go into a] basement and provide them with any information they were interested in,” he said.
When they stumbled on a photo with the Ukrainian flag on his phone, Russian soldiers asked if he was a “patriot”.
They allegedly accused him of being a “Banderite”, a derogatory term referring to Stepan Bandera, the Ukrainian nationalist leader and Nazi collaborator often evoked by President Vladimir Putin to slam Kyiv.
But Dmitry believes he ultimately had a lucky escape because Russian authorities did not view him as a threat.
By the time he arrived at a camp on the border with Estonia, he and his acquaintances were plotting their escape.
One day, they left the camp before sunrise. After two weeks of travelling, he crossed a Russian border town, and cried.
“I didn’t know where I was going,” he said.
There, he said, he had his first shower in two weeks.
“I was in the shower for an hour. It was a good feeling,” he said.
After a long journey by foot and on buses, he finally arrived in Luxembourg.
Treatment at filtration camps
More than one million Ukrainians, including the elderly and at least 240,000 children, have reportedly been sent to the Russian Federation since the start of the war, according to the United Nations and human rights groups.
The actual numbers are understood to be much higher.
“We also know about numerous kidnappings of Ukrainian citizens and their detention in Russian prisons indefinitely,” said Mykhailo Savva, who documents what he calls forced abductions at Ukraine’s Center for Civil Liberties.
The US state department’s Conflict Observatory, along with researchers from Yale University’s Humanitarian Research Lab, have identified at least 21 filtration sites in and around Donetsk, the separatist-held territory in eastern Ukraine.
Russia has denied allegations that it has abused people at the sites.
According to Ukrainians who have passed through them, there are different types of camps.
Some Ukrainians Al Jazeera interviewed said their fingerprints were taken and that they were strip-searched for “nationalistic” tattoos and photographed.
In other instances, Russian authorities confiscated their passports, searched mobile phones and downloaded contact lists, they said.
Savva said Moscow is particularly interested in identifying former Ukrainian soldiers who fought pro-Russian forces in the 2014 Donbas conflict.
He said “captured” Ukrainians continue to be “held” without legal grounds, alleging that beatings, torture, rape and arbitrary executions are widespread.
Some sites are overcrowded and facilities lack sufficient water, food or medical care, he said – accusations that are consistent with allegations by human rights groups that have documented life in the camps.
‘My mother wanted to leave, but my father refused’
When war broke out in February, Vitaly*, a 19-year-old from Mariupol, his mother and 10-year-old brother were transported to Russia by bus from the besieged city via Moscow’s so-called humanitarian corridor.
But Vitaly said there was nothing humanitarian about the evacuation, which he considers forced.
Russian occupiers intimidated residents by shooting them, he claimed.
“My mother wanted to leave, but my father refused,” he told Al Jazeera.
When Russia encircled and bombarded the Azovstal plant, where battles were fought for months, the family car exploded as it was hit by an artillery shell.
But even if the car had not been destroyed, he said it would have been impossible to leave Mariupol in it, because the Russian route was the only safe way out.
At the camp, interrogations were routine for everyone – including women, children and the elderly.
Vitaly and family were not viewed as a threat and he said the interrogators took pity on them.
They passed through a filtration camp and ended up in Russia, where they stayed for five days.
But the brief episode was so harrowing that his 10-year-old brother, who was mentally scarred, is being treated by a psychotherapist. The boy is on the mend, but Vitaly accused Russian soldiers of a lack of compassion.
“They think they are in power because they have a rifle and you don’t,” he said.
Russian authorities searched his phone and deleted photos of rocket shrapnel he had taken in Mariupol.
“I don’t think they liked it,” he said.
As Vitaly was crossing into Estonia from the Russian border town of Ivangorod, he says he was again interrogated about the war, the government and whether he had acquaintances or relatives in the Ukrainian military.
While Al Jazeera was unable to independently verify the claims of Dmitry and Vitaly, several other Ukrainians who have spoken publicly about their experiences in filtration camps have made similar accusations.
International and Ukrainian human rights groups are calling for independent investigations into the sites, but Savva said Russia has so far denied inspectors access. He called on the international community to support Ukrainian law enforcement and launch inquiries.
Meanwhile, human rights groups continue to urge Russia to stop abusing Ukrainians at these camps.
“The Office of the Prosecutor of the International Criminal Court and other relevant authorities must investigate these abhorrent crimes, including those against victims from at-risk groups,” Amnesty International Secretary General Agnes Callamard said last month.
“All those responsible for deportation and forcible transfer as well as torture and other crimes under international law committed during filtration must face justice.”