Ukraine's army is putting up fierce frontline resistance against Russian troops, but President Volodymyr Zelensky's shock dismissal of two top law enforcement officials has revealed another front in the war closer to home -- against spies and Kremlin sympathisers.
His dismissal of SBU security chief Ivan Bakanov, a childhood friend of President Zelensky, and of prosecutor general Iryna Venediktova, is unprecedented since the start of the invasion.
The decision was announced Sunday and approved by parliament on Tuesday, with Zelensky berating the pair for their failure to counter the activities of Russian spies and collaborators in Ukraine.
In his daily video address, he said there were over 650 cases involving officials suspected of treason and aiding Russia, including 60 "working against our state" in Russian-held areas of the country.
"Everyone was expecting... more tangible results" from Bakanov and Venediktova in "fighting collaborators and traitors", said Andriy Smyrnov, deputy head of the presidential administration.
- 'The last straw' -
"The president and his cabinet were not pleased with the work of Bakanov and Venediktova" even before the Russian invasion, Ukrainian political analyst Volodymyr Fesenko told AFP.
In the last few months, at least three top SBU officials have been accused of high treason.
One of them, Oleg Kulinich, who was sacked in March and was arrested on Sunday, had been based in the southern region of Kherson.
Situated close to the Crimean peninsula which was annexed by Moscow in 2014, the region was quickly taken over by Russian troops at the start of the invasion -- a significant setback for which the government was heavily criticised.
"This man was collaborating with Russian secret services. It is a very serious blow. In my view, it was the last straw for Zelensky," Fesenko said.
Zelensky had already sacked the regional head of the SBU for Kherson, Sergiy Kryvoruchko.
Another SBU official is suspected of having shared with Russian troops top secret maps of minefields intended to hamper their advance.
Zelensky on Monday said there would be a "review" within the SBU, pointing out that 28 agents could be sacked for "unsatisfactory" work.
One of Bakanov's deputies has also been sacked.
- Prisoner exchanges at risk? -
Venediktova was heading up the high-profile investigations into atrocities committed by Russian forces, particularly in the town of Bucha, which became a symbol of the alleged Russian war crimes.
According to the influential news site Ukrainska Pravda, she incurred the wrath of the presidency by attracting excessive media attention and for rushing through trials of captured Russian soldiers.
According to the report, the trials angered Moscow and made negotiations over prisoner swaps -- a priority for Zelensky -- more difficult.
For many observers in Ukraine, the reshuffle appears to have been a move to reinforce presidential control over law enforcement.
The interim replacements of both Bakanov and Venediktova -- their respective deputies -- are considered to be more politically docile.
"It is clear" that these men "will execute all the political orders" of the presidency, said Tetyana Shevchuk, an expert from the Centre for Action Against Corruption, a non-governmental organisation, cited by Forbes Ukraine.