South Korean soldiers walk past a barbed wire fence as they change guards at a watch post near the demilitarized zone separating the two Koreas in Paju, about 45 km (28 miles) north of Seoul, June 7, 2009. REUTERS/Kim Kyung-Hoon

SEOUL (Reuters) - South Korea has outlined a plan to counter a possible missile attack by North Korea, including airstrikes on a missile base, Seoul’s Yonhap News reported on Sunday citing military sources.

A scenario by the South’s Joint Chiefs of Staff submitted to President Lee Myung-bak on Saturday included a plan to counter-attack in case North Korea fires a missile targeting the South’s battleships in the contested waters off the west coast, Yonhap said.

The response under the contingency plan would be joint attacks from surface, air and sea against the North’s missile base, it said.

In late May, South Korea and the United States raised the military alert level for the peninsula after the communist North ramped up tensions by war threats, missile launches and a nuclear test.

The South’s navy earlier in June also deployed a guided-missile vessel near the sea border off the west coast. The Yellow Sea has been the site of two deadly clashes between the two rival Koreas in the past 10 years.

South Korean president Lee said on Saturday that his government would not back down to the North’s threats, saying the South has a strong defense.