South Korea expressed deep concern Friday after North Korea announced the execution of leader Kim Jong-Un's uncle. In a stunning downfall, Jang Song-Thaek -- who had been seen as Kim's political regent and the country's unofficial number two -- was executed on Thursday immediately after a special military trial, the North's state media said. "The government has deep concerns about a recent series of developments in North Korea and is watching the situation closely," the South's Unification Ministry said in a statement.