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 yesterday 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.
The reaction came after South Korean ministers related to security held a meeting to discuss Jang's execution and its implications for North Korea's future and relations with Seoul.