President Volodymyr Zelensky has sidelined his childhood friend as head of Ukraine’s security service, and another close ally as top prosecutor, in the biggest internal purge of the war, citing their failure to root out Russian spies.

Ivan Bakanov, head of the powerful SBU security agency, and Iryna Venediktova, the prosecutor general, had been emblematic of Mr Zelensky’s policy of putting young loyalists in charge of combatting corruption since sweeping to power in 2019.

But nearly five months after Russia’s invasion, the president acknowledged that his two allies had failed to root out traitors and collaborators in their organisations.

Mr Zelensky on Sunday said the two had been removed from their posts.

The deputy head of Mr Zelensky’s administration clarified on Monday that they had been suspended pending further investigation, rather than fired.

More than 60 officials from the SBU and prosecutor’s office were working against Ukraine in Russian-occupied territories, and 651 treason and collaboration cases had been opened against law enforcement officials, Mr Zelensky said in a video address.

“Such an array of crimes against the foundations of the national security of the state…pose very serious questions to the relevant leaders,” Mr Zelensky said.

“Each of these questions will receive a proper answer.”

Mr Zelensky, widely feted on the world stage as a decisive war-time leader, had been dogged before the invasion by accusations that he had named inexperienced outsiders, including friends, into jobs in which they were out of their depth.

Mr Bakanov, a friend of Mr Zelensky’s since their childhood in southern Ukraine, had helped run Mr Zelensky’s media business during his television career.

He then led the successful campaign that saw Mr Zelensky shift from playing the president on a sitcom to being elected in a landslide in real life.

Mr Venediktova, who attended a meeting just last week in The Hague discussing the international effort to prosecute Russian war crimes in Ukraine, had advised Mr Zelensky on judicial reform since he entered politics.

In his nightly speech to the nation, Mr Zelensky noted the recent arrest on suspicion of treason of the SBU’s former head overseeing the region of Crimea, the peninsula annexed by Russia in 2014 that Kyiv and the West still view as Ukrainian land.

Mr Zelensky said he had fired the top security official at the start of the invasion, a decision he said had now been shown to be justified.

“Sufficient evidence has been collected to report this person on suspicion of treason. All his criminal activities are documented,” he said.

After failing to capture the capital Kyiv early in the invasion, Russian forces used a campaign of devastating bombing to extend their control of the south and east.

In recent weeks the Russians have stepped up long-distance strikes on targets far from the front, killing large numbers of civilians in what Ukraine calls terrorism. Moscow says it is firing at military targets.

Mr Zelensky said Russia had used more than 3000 cruise missiles to date and it was “impossible to count” the number of artillery and other strikes so far.

Kyiv hopes the war is at a turning point, with Moscow having exhausted its offensive capabilities to seize a few small cities in the east, and long-range Western weapons now giving Ukraine the capability to strike arms depots behind Russian lines.

In the south, Ukraine is preparing a counterattack in coming weeks aiming to recapture the biggest swath of territory taken since the February invasion that is still in Russian hands.

In the east, Ukrainian forces withdrew at the start of July from Luhansk, one of two provinces that Russia claims on behalf of its separatist proxies.

Kyiv says Moscow is planning another assault to capture the last Ukrainian-held pocket of neighbouring Donetsk province.

Russian President Vladimir Putin launched his invasion on February 24 calling it a “special military operation” to demilitarise its neighbour and root out nationalists.

Kyiv and the West call it an attempt reconquer a country that broke free of Moscow’s rule in 1991.

-Reuters