Fighting continues in eastern Ukraine despite a ceasefire agreement reached earlier this month by European negotiators.

While Russian-backed separatists began to pull back some heavy weapons from the front lines on Tuesday as part of the deal, Ukraine says the rebels are still initiating attacks. Ukrainian forces retreated from the strategic rail hub Debaltseve last week under an onslaught from the separatists—who were bolstered by Russian troops and advanced weaponry, Western officials said—and residents now fear that the rebels could launch further attacks on the eastern cities of Mariupol and Kharkiv.