Poroshenko's office said in a statement that Ihor Kolomoysky had asked to be released from his duties as governor of Dnipropetrovsk.
The government last week followed through on its plans to dilute the power of Ukraine's ultra-rich business elite by pushing a law through parliament that led, in effect, to control over an oil and gas company being wrested from Kolomoysky.
Kolomoysky reacted by ordering armed groups of men to seize the offices of two energy companies in the capital, Kiev.
Kolomoysky is a contentious figure in Ukraine unafraid to use heavy-handed tactics in his business activities but also strongly committed to protecting Ukraine's territorial integrity.
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Over the past year, he has tapped into his wealth, which Forbes magazine estimates stands at USD 1.3 billion, to finance volunteer battalions waging war against separatist militias. Those battalions have since been subordinated to central government control, although it is believed Kolomoysky still retains considerable sway over them.
"(His) behavior was simply a slap in the face to the legitimate authorities," said Serhiy Leshchenko, an investigative journalist-turned-parliamentary deputy.
Poroshenko said that Dnipropetrovsk should continue to serve as a defensive line for eastern Ukraine.
"We must ensure peace, stability and tranquility. Dnipropetrovsk region should remain a bastion for Ukraine in the east, to protect the peace and tranquility of citizens," Poroshenko said.
When then-President Viktor Yanukovych was overthrown last year in a mass street revolt fueled in part by anger over corruption, many hoped business would no longer continue as usual.