In an appeal that may complicate European efforts to mediate the crisis, Turchynov said two “brutally tortured” bodies had been found near Slaviansk, the location of the failed Ukrainian army offensive.

One is believed to be Volodymyr Rybak, a member of Turchynov’s Batkivshchyna party, who had recently been abducted by “terrorists,” he said in a statement.

“These crimes are being carried out with the full support and indulgence of the Russian Federation,” he said. “I call on the security agencies to re-launch and carry out effective anti-terrorist measures, with the aim of protecting Ukrainian citizens living in eastern Ukraine from terrorists.”

Police said the body of a man who had suffered a violent death had been found in a river. It resembled Rybak, a local councilor in the town of Horlivka, near the regional capital of Donetsk, but they still needed to formally identify the body, they added.

Ukraine’s poorly resourced forces had previously shown little sign of taking on the gunmen who started occupying towns and public buildings two weeks ago. Turchynov’s call may not lead to much more action, but could fuel recriminations between Moscow and Kyiv about who is failing to honor the deal.

Biden told Russia on Tuesday that “time is short” for action on defusing the crisis, but Moscow refused to be rushed, saying it could handle any economic sanctions the West might impose.

Speaking in Kyiv, Biden called on Moscow to pull back troops built up on Ukraine’s borders and persuade rebels to disarm. The U.S. has repeatedly warned Russia it faces “mounting costs” if it fails to ensure full implementation of the Geneva agreement.

U.S. Army paratroopers began arriving in Poland on Tuesday to begin a series of military exercises in four countries across Eastern Europe to bolster allies in the wake of increased tensions between Ukraine and Russia.