KYIV -- Former Ukrainian President Petro Poroshenko has denounced a decision by the authorities to investigate him for high treason over his alleged financing of Kremlin-backed separatist forces in the country's east, as Kyiv's Western backers called for a fair and transparent probe.
"Accusing the head of state of state treason, financing terrorists, and facilitating terrorist organizations is a crossing of red lines," Poroshenko said in a video from the Polish capital, Warsaw.
The 56-year-old ex-president vowed to return from his trip abroad in January.
The U.S. and U.K. embassies in Kyiv said they were following proceedings "closely" and urged an independent trial.
On December 21, the State Investigation Bureau said Poroshenko had been placed under formal investigation for high treason, accusing him of "facilitating the activities" of separatists fighting government forces in a conflict that has claimed more than 13,200 lives since April 2014.
Ukraine faced an acute shortage of resources after the separatists seized territory in the Donetsk and Luhansk regions, where the country's main coal mines are located.
During his presidency, Poroshenko is suspected of helping the separatists to sell some 1.5 billion hryvnyas ($54 million) worth of coal to Kyiv in 2014-15, it said in a statement.
The politician, who is now a lawmaker and the leader of the opposition European Solidarity party, faces up to 15 years in prison if convicted.
"The United States is closely following the case against former President Poroshenko," the U.S. Embassy wrote on Twitter. "Crucial that process and outcome be based on the rule of law, not politics."
British Ambassador to Ukraine Melinda Simmons tweeted it was "vital" that the case be tackled "independently, impartially, and professionally, ensuring fairness and respect for due process."
Officials have said the accusations against Poroshenko were related to similar charges against pro-Russian lawmaker Viktor Medvedchuk, who has been under house arrest since May.
In October, Prosecutor-General Iryna Venediktova accused Medvedchuk of colluding with officials during Poroshenko's administration to buy coal from mines located in separatist-held areas as a way to finance the separatists. His political party is the second largest in parliament.
Poroshenko's and Medvedchuk's political parties dismissed the accusations, calling them an effort to divert attention from President Volodymyr Zelenskiy's government's own wrongdoing and failures.
Zelenskiy succeeded Poroshenko as president after defeating him in a 2019 election.
