Scott Olsen/Getty Images
About 500 pro-Russian separatists attacked a border control office in eastern Ukraine on Monday, using rocket launchers and automatic weapons. Five rebels were killed and another eight wounded; seven border guards were wounded. It was the biggest assault on the country's border with Russia since the separatist revolt began. As The New York Times notes, this could spell trouble for Ukraine's president elect Petro O. Poroshenko, who has vowed to crush the rebellion.