President Park Geun-hye on Thursday dismissed her top security aide and the chief of National Intelligence Service as part of her government overhaul in the wake of last month's ferry disaster.
She accepted the recently tendered resignations of NIS director Nam Jae-joon and National Security Office chief Kim Jang-soo, the presidential office said.
The move came amid rising calls for a personnel overhaul to restore public trust in the government that has been eroding due to its inept response to the nation's worst maritime disaster in two decades.
Their replacements will soon be announced, presidential spokesperson Min Kyung-wook told reporters. NIS First Vice Director Han Ki-beom and National Security Office Deputy Chief Kim Kyou-hyun will fill in for the interim, he said.
Kim has been under fire for his recent remarks denying the role of his office in handling social disasters. The remarks were perceived as "irresponsible" at a time when the nation was grieving over the safety fiasco that left over 300 people dead or missing.
The announcement of Nam's resignation was somewhat a surprise as he was largely believed to retain his post given that he is one of Park's most trusted aides.
Nam has been at the centre of the opposition parties' attack due to a series of scandals involving the chief intelligence agency. The agency has taken flak for interfering in the 2012 presidential election, revealing a transcript of a 2007 inter-Korean summit and fabricating court evidence in an espionage scandal.
The resignations of the two former Army generals presaged a major shift in the lineup of Seoul's security and foreign affairs staff. Some observers raised the possibility that Seoul's stance toward Pyongyang would become more flexible.
Nam, a former general senior to Kim, is known to oppose the transfer of wartime operational control, favour a strengthening of the South Korea-US alliance and stick to a hard-line stance regarding denuclearization of the North.
It is speculated that in the follow-up reshuffle, President Park will also replace Defence Minister Kim Kwan-jin, who has served at the post since December 2010.
As President Park has vowed to conduct a complete overhaul of the national system to overcome the maritime tragedy, calls have been increasing for a reorganisation of the top government echelons, particularly those handling national security and safety.
But some observers expressed concern that too drastic a reshuffle could negatively influence the management of national security when Pyongyang is sticking to its nuclear adventurism with the threat of conducting another atomic test.