KIEV, Ukraine (AP) — A Ukrainian court has ruled that the 2016 nationalization of a major bank owned by a powerful tycoon was illegal.

The court in Kiev ruled on Thursday that Privatbank, owned by tycoon Ihor Kolomoyskyi, was nationalized in 2016 illegally.

It was not immediately clear how the government would return the bank, once Ukraine's biggest private lender with a reported capital shortfall of $5 billion, to Kolomoyskyi.

Ukraine's National Bank vowed to appeal the ruling.

Kolomoiskyi's figure has loomed large in Ukraine in the past few weeks as the country goes to the polls to elect a new president Sunday. Kolomoyskyi is an archrival of incumbent President Petro Poroshenko. The tycoon is believed to have ties to Volomyr Zelenskiy, a comedian who emerged as an odds-on favorite in the race.