A combination of pictures show Russian President Vladimir Putin (L) and his Ukrainian counterpart Petro Poroshenko.

MOSCOW, June 9 (Xinhua) -- Russian President Vladimir Putin and his Ukrainian counterpart Petro Poroshenko discussed the exchange of detainees in a phone call on Saturday.

"They highlighted humanitarian issues, including the exchange of detainees. Vladimir Putin pointed out the importance of releasing the Russian journalists arrested in Ukraine without delay," the Kremlin said in a press release.

Putin and Poroshenko agreed that the two countries' human rights commissioners should visit Russian citizens detained in Ukraine and Ukrainian detainees in Russia, the Kremlin said.

On May 15, the Ukrainian Security Service raided RIA Novosti Ukraine news agency, accusing its staff members of high treason. Its chief editor Kirill Vyshinsky, a Ukrainian native with Russian citizenship, was detained.

According to a TASS report, Ukrainian Presidential Envoy for the Peaceful Settlement of the Situation in the Donetsk and Lugansk Regions Irina Gerashchenko said that Kiev is ready to hand over 23 Russians in exchange for four Ukrainian citizens.

Russia and Ukraine, with close ties in history, are at odds with each other over Crimea and alleged Russian involvement in the armed conflicts in southeast Ukraine.