North Korea’s military has threatened to turn South Korea’s Presidential Office of Cheong Wa Dae into a “sea of fire” a day after the South held a military drill near Yeonpyeong Island. The South’s military exercise was held to mark the first anniversary of the North’s shelling of the island.

North Korea's Korea Central News Agency reports on Thursday the North Korean military's statement that if South Korea fires a single shot into North Korean territory, a sea of fire similar to that seen last year on Yeonpyeong Island will engulf South Korea’s presidential office.

The North also claimed that its artillery attack on Yeonpyeong was a legitimate self-defense measure, describing the South’s military drill on Wednesday as a war rehearsal against the North and another political and military provocation.

Political analysts say that it would have been difficult for the North to stay calm to the South’s military drills, and the sea of fire warning is linked to the Wednesday remarks by President Lee Myung-bak at the Northwestern Islands Defense Command that the North has made no official apology for the Yeonpyeong attack.

Pyongyang has not given any response to Seoul after Unification Minister Yu Woo-ik has sent series of signals to resume dialogue and has taken a number of conciliatory measures since he took office in September. Some analysts say the North appears to be pressuring Seoul to change its fundamental policy towards the North by specifically referring the Presidential Office of Cheong Wa Dae in its threat.