Ex-President and European Solidarity Party leader Petro Poroshenko has said he is upset about the leak of materials from Ukraine's State Bureau of Investigations (SBI). He said he does not rule out that the information is going to Russia.

"We are concerned that there is a constant leak of each material, which the SBI receives, to the address of Mr. [Andriy] Portnov [ex-deputy head of the Presidential Administration under ex-President Viktor Yanukovych] and not only him. We do not rule out that such materials are making their way outside the borders of Ukraine in the direction of Russia," Poroshenko told journalists after being questioned by the SBI on Thursday.

Poroshenko said his team had addressed these concerns with the SBI.

"If the SBI is prejudiced and does not open a case against Portnov for making false statements about a crime, we will seek the truth for defending Ukraine. We are not talking here about defending Poroshenko, but about defending Ukraine in court," Poroshenko said.