The South Korean military began its annual war exercise involving all branches of service on Monday to bolster its defense posture against belligerent North Korea, the Joint Chiefs of Staff (JCS) said.

This year's 12-day Hoguk exercise involving the Army, Navy, Air Force and Marine Corps "will focus on ways to establish supreme military defense capabilities against (North Korea's) possible regional provocations and all-out war," the JCS said in a statement.

The exercise was to be conducted across the nation, the JCS said, adding that the programs include joint landing drills, maritime infiltration defense drills and those to defend the northwestern islands on the Yellow Sea. Some U.S. military forces will also join some of the drills, according to the JCS.

Some 330,000 military servicemen are taking part in the drill, the largest ever number since the country first staged the drill in 1996, according to the JCS officers. The exercise used to involve some 80,000 service personnel.

"As North Korea is believed to have carried out intensive military drills in recent months, we've decided to launch the largest-ever scale of the drills in response in order to boost our capabilities," said a JCS officer, requesting anonymity.   

On Friday, Pyongyang bashed Seoul for the planned drill, claiming that the South has "sought a chance to ignite a war" and has become "more bellicose and provocative."

In response, Seoul's defense ministry spokesman Kim Min-Seok stressed that the Hoguk drill "has been conducted on an annual basis since 1996 to boost joint posture and coordination between the different branches of the military."

The Koreas remain technically at war after the 1950-53 Korean War ended in an armistice, not a peace treaty. About 28,500 U.S. soldiers are stationed here to deter and counter potential threats from the communist country. (Yonhap)