Reporting from Donetsk, Ukraine — In a sign of the deepening destabilization of eastern Ukraine, the popular mayor of Kharkiv, the country’s second-largest city, was shot in the back on Monday, authorities said. Mayor Gennady Kernes was in critical condition after undergoing surgery at a local clinic, said Dr. Valery Boiko, who performed the two-hour operation. He was shot while jogging on the outskirts of Kharkiv at about noon, according to a statement posted on the city's website. A police report said he was cycling at the time. “The doctors qualified the injury as heavy, given the damage to internal...