South Korea’s President Park Geun-hye on Monday promised a strong military response to any North Korean provocation after Pyongyang announced that the two countries were now in a state of war.

Ms. Park’s warning came as North Korea’s rubber-stamp Parliament formalised the status as a nuclear weapons state and appointed a sacked economic reformer for a fresh term as Prime Minister.

It also coincided with a U.S. announcement that it had deployed stealth fighters to South Korea as part of an ongoing joint military exercise.