Ukraine's registry for court decisions placed the August 15 ruling of Kyiv's Solomyanka District Court on its website on August 21, saying that the ruling cannot be appealed.
It is not clear what charges Poroshenko and Klimkin are facing.
According to the court ruling, the case was initiated by an unidentified individual.
In recent weeks, Poroshenko was questioned twice as a witness by the State Bureau for Investigations in a tax evasion case.
Poroshenko lost a reelection bid in April to Volodymyr Zelenskiy.
A day after Zelenskiy's inauguration in May, Andriy Portnov, a former deputy head in the administration of ex-Ukrainian President Viktor Yanukovych, returned to Ukraine from self-imposed exile abroad and filed several lawsuits against Poroshenko, accusing him of economic crimes and illegal attempts to retain power, among other things.
A billionaire confectioner, Poroshenko and his party successfully ran on a pro-European, anti-Russian ticket in July parliamentary elections, winning 25 seats.
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