A Ukrainian serviceman walks next to remains of a Russian Tochka U ballistic missile, as Russia's attack on Ukraine continues, in Kharkiv region, Ukraine, in this handout picture released April 23, 2022.  Press service of the Ukrainian Ground Forces/Hando
A Ukrainian serviceman walks next to remains of a Russian Tochka U ballistic missile, as Russia's attack on Ukraine continues, in Kharkiv region, Ukraine, in this handout picture released April 23, 2022. Press service of the Ukrainian Ground Forces/Handout via REUTERS . Reuters / UKRAINIAN GROUND FORCES

As Ukraine hunts for traitors, the fear of Russian infiltration extends east, far from the capital.

The sense of paranoia runs deepest here, in eastern Ukraine, where suspicions of treason committed by locals divide formerly occupied villages like Kutuzivka, a once-sleepy hamlet east of Kharkiv, where signs of a recent Russian presence are everywhere.

Stray dogs roam over broken glass as the sound of shelling echoes overhead, with Ukrainian troops still fighting off a near-constant barrage of artillery fire by Russian troops north of the village when Reuters visited at the end of May.

When Russian troops arrived in Kutuzivka in early March, they quickly set up a local puppet administration.

Nataliia Kyrychenko, a 55-year-old farm owner in the village, was hiding in her house with several neighbours when Russian soldiers came to her door. Villagers said a Russian commander brought Kyrychenko and her neighbours out onto the street and informed them that a local woman named Nadiia Antonova would now head the village.

Kyrychenko said she was interrogated for two days by Russian forces about her son-in-law, who is in Ukrainian law enforcement. The soldiers told her, Kyrychenko recounted to Reuters, that Antonova had informed them about her son-in-law and accused her of working as a spotter for Ukrainian troops, tasked with tracking movements of Russian soldiers.

"When the Russian soldiers took me away I honestly didn't think I would come back," she said. "I couldn't believe that someone in our community would turn me in."

Kyrychenko was eventually released. Russian officials at the Kremlin did not respond to Reuters' questions about the case.

In late April, Ukraine successfully pushed back Russian troops and liberated Kutuzivka. Antonova was swiftly detained and placed under criminal investigation for collaborating with Russian soldiers. She faces more than a decade in jail if convicted. Antonova's lawyer did not respond to Reuters' questions.

In a speech earlier this month, President Volodymyr Zelenskiy spoke about the high toll Russian infiltration was taking on the country. Below the highest levels of treason he highlighted, there are many more cases that fall into a grey area. These cases can range from those who post pro-Russian content on social media to those who cooperate in any way with occupying Russian troops.

"Our population played a very big role in informing police, alerting us to saboteurs," said Yevhen Yenin, the first deputy minister of the internal affairs ministry, which oversees the national police.

Though the Security Service of Ukraine (SBU) is officially tasked with investigating such cases, much of the practical work of gathering information has fallen to the police, Yenin said.

The National Police have so far detained more than 1,000 people suspected of sabotage and reconnaissance activities on behalf of the Russian authorities, according to the internal affairs ministry.

In Kharkiv, about 40 kilometres from the Russian border, four police officers began their night patrol just after the city's 10 p.m. curfew in late May. Touting AKs and wearing bulletproof vests, the officers scoured the city's darkened streets for suspicious figures.

"Whenever we stop anybody we try to understand where they live, to identify who they are, and whether they speak Ukrainian or not," said Tymur, who declined to give his last name.

Their car sped up as an air raid siren howled overhead. The officers made their way down into a subway station for shelter. Fifteen minutes later, they reemerged to patrol the deserted streets until dawn.

Antonova's case has attracted attention in Russia. Margarita Simonyan, editor-in-chief of Russian state television channel RT, said on television that Antonova had helped the Russian operation and was now being unfairly punished. "We need to save those we can save, and reward those who need to be rewarded," Simonyan said.

In an indication of the complexities of such cases, some villagers also say Antonova is being unfairly targeted. They say Antonova ensured that villagers had food and protected them from mistreatment by Russian soldiers during the occupation.

"Can you call it collaboration when the Russians are putting their guns against her back?" one resident shouted outside of a kindergarten where a dozen villagers still live underground.

But regional chief prosecutor Oleksandr Filchakov said investigators had evidence Antonova fed information to the enemy that led to the deaths of Ukrainians. While he acknowledged the sympathies of some villagers, Filchakov said Ukrainians needed justice.

"She must be held responsible," he said.