South Korea and the United States on Monday began their annual military drills as planned in a relatively low-profile manner, as families separated by the 1950-53 Korean War were reunited amid warming inter-Korean ties. 

The much-anticipated Key Resolve and Foal Eagle exercises took place despite Pyongyang's repeated calls earlier this month for their cancellation at the threat of scrapping the reunions. The North later agreed to go ahead with the cross-border event, in what was seen as a concession aimed at improving ties. 

The two-week Key Resolve is a computer-based command post exercise, involving about 10,000 South Korean and 5,200 American forces, with 1,100 coming from overseas U.S. bases. 

Foal Eagle is a combined field training drill, in which 7,500 American troops, including 5,100 from abroad, carry out a set of ground, air, naval, expeditionary and special operations. IT runs through April 18.

While some 200,000 South Koreans attended last year's Foal Eagle, the number of participating forces has decreased this year as some soldiers have been mobilized to help contain the outbreak of bird flu and support disaster relief, including removing record levels of snow in the east coast that have claimed several lives. 

This year, Key Resolve will apply the joint deterrence plan detailing 30 types of North Korean provocations, which was signed by the two nations' Joint Chiefs of Staff a year ago amid heightened tension, according to military officials.

The routine drills have once again drawn fierce criticism from the Pyongyang as hundreds of South Koreans were reunited with elderly relatives from the North over the weekend. The second round of tearful reunions has been under way since Sunday to last until Tuesday. 

On Sunday, the North's state-run Rodong Sinmun newspaper quoted a North Korean official at the United Nations Charter meeting last week as saying the U.S. was the "main culprit" for proceeding with the military exercise.

A South Korean military official said the drills will be held in a "low-key" manner considering the ongoing reunions, without involving high-profile nuclear bombers and carriers so as not to provoke the North. 

"The South Korea-U.S. drills are aimed at defending the Republic of Korea in time of war," defense ministry spokesman Kim Min-seok said, noting the exercise will be held at a similar level as last year. 

About 28,500 U.S. troops are stationed in South Korea to help deter North Korean aggression. South and North Korea remain technically in a state of war as the Korean War ended in a ceasefire, not a peace treaty. (Yonhap)