KYIV, Ukraine — Even as it engages in fierce fighting with Russia on the battlefield, Ukraine is also waging war on a different, more shadowy front: rooting out spies and collaborators in government and society who are providing crucial help to the invading forces.
While Ukrainian society as a whole has rallied to the country’s defense, Russian sympathizers are reporting the locations of Ukrainian targets like garrisons or ammunition depots, Ukraine’s officials say. Priests have sheltered Russian officers and informed on Ukrainian activists in Russian-occupied areas. One official said collaborators had removed explosives from bridges, allowing Russian troops to cross.
The issue was cast into sharp relief on Sunday night when President Volodymyr Zelensky dismissed two senior law enforcement officials, saying they had not been nearly aggressive enough in weeding out traitors. It was the first major reshuffle of his brain trust since the war began.
Hundreds of treason investigations have been opened, Mr. Zelensky said in a televised address after the dismissals, which still must be confirmed by the Parliament, underscoring the depth of a problem that can provide a critical advantage to the enemy. The threat from spies in government, churches and intelligence agencies, and from Russian-leaning citizens in the East, has plagued Ukraine for years, but has become still more acute during the war.
Mr. Zelensky specifically cited Ukraine’s security service, an unwieldy force of 27,000 personnel, the largest in Europe. Western allies believe the service has too many areas of operation, leaving it open to corruption, and prone to straying from its spy-hunting role.
“Such an array of crimes against the foundations of the national security of the state, and the connections detected between the employees of the security forces of Ukraine and the special services of Russia, pose very serious questions to the relevant leadership,” Mr. Zelensky said.
One of the officials Mr. Zelensky ousted on Sunday was the head of the domestic intelligence agency, Ivan Bakanov, a childhood friend of the president. The other was Iryna Venediktova, Ukraine’s prosecutor general. While Mr. Zelensky did not accuse them of betrayal, he suggested they had turned a blind eye to traitors in sensitive positions.
“Actions and any inaction of each official in the security sector and in law enforcement agencies will be evaluated,” Mr. Zelensky said.
The deputy head of the president’s office, Andriy Smirnov, was more pointed on Monday, saying the two officials were ousted for failing to “cleanse” their agencies of collaborators.
“Everybody for a long time waited for more concrete, and maybe radical results,” Mr. Smirnov said. “At the same time, in the sixth month of the war we are still turning up wads of such people.”
The intelligence service poses a particular problem for Ukraine because many of its chiefs graduated from K.G.B. schools, said Volodymyr Ariev, a member of Parliament in an opposition party that accused Mr. Zelensky of inaction on the issue before the dismissals on Sunday.
“Of course, it’s not an easy task,” Mr. Ariev said. “They are not walking in the corridors with a badge saying ‘I am K.G.B.’”
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The United States and its allies have provided vast quantities of intelligence data to Ukraine during the war, but American officials say the officials’ dismissals were not due to any mishandling of that information.
The reshuffling of top security positions provided the first outward sign of divisions in Mr. Zelensky’s team, which had been remarkably cohesive during the war. Ukrainian media and opposition politicians suggested alternative reasons for the shake-up, including Ms. Venediktova’s rising international profile as an aggressive prosecutor of war crimes; some officials fear these trials could lead to retaliatory prosecutions of Ukrainian prisoners in Russia’s hands.
Mr. Zelensky said that more than 60 prosecutors and domestic intelligence agents had remained in Russian-occupied territory after the invasion and were collaborating with Moscow. He said the authorities had opened 651 criminal investigations of police officers, prosecutors and other security officials.
More than 800 people suspected of engaging in sabotage and reconnaissance for the Russians, many of them civilians, have been detained and handed over to the Security Service of Ukraine since the war began, Yevhinnii Yenin, first deputy minister of internal affairs of Ukraine, said last month.
The Ukrainians recently foiled a Russian plot to target the leadership of the Ukrainian government, Mr. Yenin said. And law enforcement agencies now operate 123 counter-sabotage groups comprising a total of at least 1,500 members, he said.
Out in the villages and towns on the frontline of the war in eastern Ukraine, the most pro-Russian region of the country, soldiers worry continually about the threat posed by enemy sympathizers reporting their positions or helping direct Russian artillery fire.
Russia’s battered forces have paused their drive to seize territory in the region, but continue to use their numerical advantage in artillery to batter Ukrainian towns and military units. A renewed offensive is expected before long.
By the height of the fighting for the eastern city of Lysychansk last month, most civilians had fled, but significant portions of those who remained showed open disdain for the Ukrainian defenders. “We are a Russian nation,” said one resident in the city’s market who declined to provide his name. “You can kill us, but you can’t defeat us.”
The Kremlin has shut down independent news organizations, feeding a distorted picture of Ukraine and the war to viewers in Russia and sympathizers in eastern Ukraine. But on Monday, one of the most important prewar Russian outlets, TV Rain, resumed broadcasting on YouTube from Riga, Latvia.
Ruslan Osypenko, the police chief of Ukraine’s Donetsk region, which has been subjected to increasingly intense artillery attacks, said that tracking and detaining suspected informants was one of his top priorities. His force has a unit dedicated to monitoring social media channels to detect people passing information on military activities and targeting to Russian forces.
Informants are of alltypes, he said, and often act on the promise of a position in a future, Russian-controlled administration. “They can be young and old,” he said in an interview Monday in his temporary base in the city of Pokrovsk. “The Russian special services are working in this direction, we know that.”
Mykyta Poturaiev, a Ukrainian lawmaker who recently convened a parliamentary committee to investigate collaboration, said that Orthodox priests loyal to Moscow had given pro-Russian sermons, provided Russians tips on targets, and informed on Ukrainian activists.
“One example is very illustrative,” Mr. Poturaiev said. In one Russian-occupied village, he said, a priest helped billet Russian officers in local houses and arranged for a warehouse to store ammunition.
But infiltration of the domestic intelligence service and prosecutors’ office — the very agencies that are intended to find and prosecute traitors — is particularly insidious.
In his decree dismissing Mr. Bakanov, Mr. Zelensky cited an article under martial law that pertains to “failure to perform service duties, which led to human casualties or other grave consequences.”
The decree did not specify what casualties or consequences, but speculation swirled in Kyiv on Monday that Mr. Bakanov had been ousted for glaring intelligence failures in the first days of the war in the southern city of Kherson, which the Russians captured almost without a fight. Local officials in Kherson switched sides, and explosives were removed from bridges around the city, Mr. Ariev, the opposition member of Parliament said.
In late March, Mr. Zelensky stripped two generals of the security service of their ranks, calling them traitors; one was in charge of the Kherson region and the other fled Ukraine on the eve of the invasion, only to be apprehended months later in Serbia, accused of trying to smuggle cash and emeralds into the country.
One Parliament member, Oleksiy Honcharenko, who is not affiliated with a party, said of Mr. Zelensky’s reference to “grave consequences,’’ “Translation: for the surrender of Kherson.”
The security service, known by its Ukrainian initials S.B.U., is the country’s main domestic security and intelligence authority, Ukraine’s successor to the Soviet-era K.G.B. Its vast size has drawn criticism — by comparison, Britain’s MI5 has just 4,400 employees, according to the Atlantic Council — and it has long faced calls for reform.
Business groups have said that the service shook down companies for bribes and that corrupt agents, compromised and facing possible prosecution, became easy marks for recruitment by Russia.
“Surprise, surprise,” Serhiy Fursa, an analyst with Dragon Capital, a leading Ukrainian investment bank, wrote on Facebook of Mr. Zelensky’s charges of treachery in the service. “What lesson did this war give us? A corrupt man is Putin’s best friend.”
Reporting was contributed by Carlotta Gall from Druzhkivka, Ukraine; Thomas Gibbons-Neff from Dubai; Natalia Yermak from Lviv, Ukraine; Maria Varenikova from Kyiv; and Marc Santora from London.