U.S. Vice President Joe Biden and Ukrainian President Petro Poroshenko called Friday for a resolution in the conflict with pro-Russian separatists in eastern Ukraine.
A White House statement said Biden and Poroshenko spoke by telephone and "expressed deep concern over the recent surge in fighting in eastern Ukraine, where cease-fire violations by combined Russian-separatist forces are at their highest levels since 2015, often using heavy weapons."
The White House said Biden "relayed that the United States had sent a message to Russia that the world is watching and underscored the need to de-escalate the situation." It said the vice president also urged Ukraine to "show restraint."
Biden and Poroshenko also "reiterated the need for a political and diplomatic resolution of the conflict through full implementation of the Minsk agreement by all parties."
Ukrainian officials said Thursday pro-Russian separatists "launched more than 500 mortar and over 300 artillery shells" at Ukrainian positions in eastern Ukraine, killing at least three Ukrainian soldiers and wounding six more.
Poroshenko warned Thursday his country has not ruled out martial law or a new wave of military mobilization if the fighting continues.
Russia recently accused Ukrainian military and intelligence forces of plotting attacks in the annexed region of Crimea.
Ukraine officials have denied the accusations, saying the Kremlin was likely to use it as a pretext for a major escalation of the more than two-year-old conflict in eastern Ukraine.