A cease-fire was declared in eastern Ukraine at a minute after midnight Sunday, kindling slender hopes of a reprieve from a conflict that has claimed more than 5,300 lives.
But within two hours of the cease-fire's scheduled start, the warring sides were already trading accusations of fresh attacks.
Under an agreement struck last week, both Ukrainian forces and Russian-backed separatist rebels were to hold their fire as of one minute after midnight on Sunday (5:01 p.m. Saturday ET). If that holds, both sides are to begin pulling back their heavy weaponry to form a wide buffer zone.
Ukrainian President Petro Poroshenko said in a Twitter message that, "The entire world holds its breath in anticipation," of the ceasefire. But he also warned, "If slapped on one cheek, we won’t turn the other one."
President Barack Obama spoke with Poroshenko in a telephone call Saturday and both leaders pledged to remain in contact in the coming days. Obama expressed his “deep concern about the ongoing violence, particularly in and around Debaltseve," the White House said.
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The U.S. State Department said commercial photos showing multiple rocket launchers and artillery around around Debaltseve is evidence Russia is aiding the separatists. "We are confident that these are Russian military, not separatist systems," State Department spokesperson Jen Psaki said.
Both sides accused the other new attacks Sunday.
Ukrainian security services chief Valentyn Nalyvaichenko said one infringement was reported about 50 minutes after the deadline. Artillery salvoes were fired from an area that Nalyvaichenko said is under the control of a Cossack unit manned by Russian citizens.
Meanwhile, rebels accused the Ukrainians of deploying artillery shortly after midnight.Donetsk News Agency, a separatist mouthpiece, cited senior rebel defense official Eduard Basurin as saying the Ukrainian forces garrisoned in Debaltseve fired artillery and mortars at rebel positions.
On Saturday, intense fighting persisted around the strategic government-held railway hub of Debaltseve, which has been besieged by separatist forces.