© ReutersRoman Nasirov
The government said on March 3 that State Fiscal Service (DFS) Director Roman Nasirov has been temporarily relieved of his duties.
Meanwhile, a special prosecutor tasked with fighting corruption said he will seek Nasirov's arrest on suspicion of "abuse of office leading to serious financial losses," voicing concern that he could try to flee the country.
The moves came a day after the National Anticorruption Bureau (NABU) said it attempted to serve Nasirov, who was in a Kyiv hospital, with a document identifying him as a suspect.
Minutes later, Nasirov was transferred to an intensive care unit after suffering what a doctor said was a heart attack.
The Specialized Anticorruption Prosecutor's office (SAP) says it suspects Nasirov might have helped fugitive lawmaker Oleksandr Onyshchenko dodge taxes.
Onyshchenko, who fled Ukraine before being stripped of his parliamentary immunity from prosecution last summer, claims to have recorded conversations detailing corruption involving Poroshenko and his allies.
He is wanted in Kyiv on suspicion of fraud and of embezzling the equivalent of more than $100 million in tax revenues from natural gas delivery contracts.
Nasirov's lawyer, Oleksandr Miroshnik, said on March 3 that his client remained unconscious following surgery. He said that Nasirov had already been ill and that his hospitalization has nothing to do with the ongoing investigation.
Miroshnik added that NABU's "attempt" to hand the document to Nasirov to inform that he is a suspect was conducted illegally.
The pro-Western government that came to power after protests known as the Euromaidan pushed Moscow-friendly President Viktor Yanukovych from power in 2014 has been under pressure to tackle corruption and reform the economy.
Poroshenko has pledged to root out graft, but no senior official has been successfully prosecuted for corruption by his government.
Comment: Is Kiev desperately trying to save some face after the US proposes to cut funding in half and their Central Bank chair is considering resigning?