South Korea has threatened to bomb North Korea if it repeats last week's artillery attack that killed four people.
Kim Kwan-jin, a retired general, was speaking at a parliamentary meeting confirming him as new defence minister.
Mr Kim said: 'If there are further provocations, we will definitely use aircraft to bomb North Korea.'
His comments come a day after US Secretary of State Hillary Clinton said North Korea threatened the region and the world.
North Korea shelled an island near their disputed border, killing two South Korean marines and two civilians.
Defence Minister Kim said the attack led to the most serious crisis since the Korean War, but he saw little chance strong retaliation from the South would lead to a full-blown war.
'It will also be difficult for North Korea to conduct a full-scale war because there are some elements of insecurity in the country, such as the national economy and power transfer.'
The North has more than 5,000 multiple-launch rockets pointed at the capital Seoul, which, with its satellite cities, is home to some 25m people. South Korea has about 490 combat aircraft.
The foreign ministers of the US, Japan and South Korea will meet in Washington on Monday to discuss North Korea.