President Lee Myung-bak's choice for new defence minister said that South Korean jets will bomb North Korea if Pyongyang stages an attack similar to last week's deadly artillery barrage.
The tough words came as Mr Lee's government suffered intense criticism that the response to the North's November 23 shelling on a South Korean island was weak, and over a stunning revelation that the South's spy chief dismissed information in August indicating that North Korea might attack the front-line island.
Lee's nominee, Kim Kwan-jin, told a parliamentary confirmation hearing that North Korean aggression will result in airstrikes. He said South Korea will use all its combat capabilities to retaliate.
"In case the enemy attacks our territory and people again, we will thoroughly retaliate to ensure that the enemy cannot provoke again," Mr Kim said. The hearing is a formality as South Korea's National Assembly does not have the power to reject Mr Lee's appointment.
Kim said it will be difficult for North Korea to conduct a full-scale war because of its weak economy and worries over the success of a plan to transfer power from leader Kim Jong Il to his young, untested son, Kim Jong Un.
Despite the bold declarations, questions have been raised about Mr Lee's readiness - and even willingness - to stand up to the North. The president has been criticised for leading a military whose response to the attack was seen as too slow and too weak. The North fired 170 rounds, compared with 80 returned by South Korea.
Satellite photos showed only about 10 South Korean rounds landed near North Korea's army barracks along the west coast, according to the office of lawmaker Kwon Young-se, who said he saw the images provided on Thursday by the National Intelligence Service.
Also Friday, South Korea's Yonhap news agency reported that North Korea has boosted the number of multiple-launch rockets capable of hitting Seoul. Yonhap, citing an unidentified South Korean military source, said North Korea's rockets have increased by 100 pieces to about 5,200.
The South Korean Joint Chiefs of Staff said it could not confirm the report because it involves military intelligence.