Poroshenko has been indicted for high treason over his involvement in trading coal with the separatists in the eastern Ukrainian breakaway region of Donbas.
A Kyiv court on Thursday ordered an assets freeze against former Ukrainian President Petro Poroshenko as part of an investigation into "high treason," the prosecutor general's office announced.
Poroshenko, president from 2014 to 2019 and now 56, is accused of facilitating the purchase of coal from companies in eastern Ukraine controlled by pro-Russian separatists at war with Kyiv.
"The court decided to seize the suspect's assets," including his real estate and shares in companies, the prosecutor's office said in a statement.
Poroshenko, who is currently abroad and has promised to return to Ukraine on January 17, had no immediate comment on the decision.
The former president has repeatedly denied any "treason" and accused his successor, Volodymyr Zelenskyy, of being behind his legal troubles.
Before the announcement of the decision on Thursday, Poroshenko had written on Facebook that he would "return to Kiev" to appear before a judge, "not to (defend himself), but (...) to defend Ukraine against his incompetent government."
Specifically, he is suspected of having helped the self-proclaimed republics of Donetsk and Lugansk in eastern Ukraine to sell coal to Kyiv in 2014 and 2015 for a total amount of about 48 million euros.
Last month, the former leader who currently serves as an MP at the Ukrainian Rada failed to appear for questioning in connection with this investigation.
The war in eastern Ukraine, which began in 2014, is an ongoing conflict between the Ukrainian army and Russian-backed separatists in the Donetsk and Luhansk regions.
The seven-year war has seen about 14,000 casualties, while more than 2 million Ukrainians have sought refuge either in other parts of the country or abroad.