Russian President Vladimir Putin and Ukrainian Volodymyr Zelinsky discussed new prisoner exchange, after a first such operation took place in September and another in December with separatists loyal to Russia, Kiev announced Friday.

The Ukrainian presidency announced in a statement that the two presidents discussed in a phone call to “liberate detained Ukrainian citizens” in the lands of separatists in eastern Ukraine and Crimea, as well as Russia.

According to the same source, Zielinski and Putin also discussed preparation for a new meeting following their meeting in Paris in December and held under French-German mediation.

After the first meeting between them, a process of exchanging about two hundred prisoners occurred between Kiev and the pro-Russian separatists in an operation that falls within the framework of reducing escalation in this frozen armed conflict in large part, but it has resulted in more than 13 thousand people killed since 2014.