Ukrainian authorities launched a criminal case against the head of the Border Service of the Russian Federation, even as Ukraine’s President Petro Poroshenko awaits meeting with Russian officials and leaders of the Organization for Security and Cooperation in Europe, or OSCE, to discuss ways to resolve the ongoing crisis in the eastern reaches of his country.

The decision to open criminal proceedings against the Russian official came as retaliation for the killing of 13 Ukrainian troops Friday in clashes with pro-Russian forces. While Kiev has claimed Moscow is fueling the feud by providing arms and ammunition to the separatists, Ukrainian authorities are attempting to get those same separatists to negotiate Saturday for a cease-fire to curb the increasing violence in the eastern region.

“Today, the Security Service of Ukraine ... has started criminal proceedings against the head of the Border Service of the Russian Federation. He also holds the office of the deputy director of the Federal Security Service of Russia,” Valentyn Nalyvaichenko, the head of the Security Service of Ukraine, said in a statement, according to Interfax-Ukraine, a local news agency.

Russia has denied Ukraine’s accusations, which were reportedly seconded by the U.K., and said the claims were “shameless,” China’s Xinhua news agency reported.

Poroshenko spoke with Catherine Ashton, the European Union’s high representative for foreign affairs and security policy, about the Ukraine-Russia-OSCE meeting scheduled for Saturday. Those at the meeting reportedly will discuss ways to curb the ongoing violence, such as a new cease-fire. Poroshenko has also reportedly talked to German Chancellor Angela Merkel and French President Francois Hollande about his country’s current plight.

“The head of the state assured that, as a part of the Berlin agreements between the foreign ministers of four countries, Ukraine is prepared for the further work of three-party contact group, in particular, to conduct another meeting on July 5. Ukraine has proposed venue for the meeting and is waiting for confirmation from the other side,” Interfax-Ukraine reported, citing Poroshenko’s press representative.

Meanwhile, Natalia Galibarenko, Ukraine’s first deputy minister of foreign affairs, met with Danielle Auroi, chairman of the French National Assembly’s Committee on European Affairs, to ensure the smooth implementation of a deal struck between the EU and Kiev, which would help the country revive its economy, the Ukrainian government said in a statement Friday.