South Korean soldiers fired warning shots Monday as a North Korean patrol neared the heavily guarded border between the countries, local media reported.

National news agency Yonhap quoted a Joint Chiefs of Staff (JCS) officer as telling reporters, “Some ten North Korean soldiers came close to the military demarcation line in the northern city of Paju at around 9:40 a.m. today."

The soldiers from the North were taking pictures of signposts set to mark the demilitarized zone, he added.

The North Korean side, however, did not return fire as the patrol moved away from the military demarcation line, according to the JCS.

The officer said no further unusual movements had been detected after the North Korean troops retreated entirely around three hours later.

The encounter occurred as South Korea’s military kicked off its two-week annual drills involving all branches of service, aimed at bolstering defense against possible threats from the North.

On Friday, Pyongyang criticized Seoul for the planned drill and for becoming "more bellicose and provocative," Yonhap reported.

The South’s defense ministry spokesperson, Kim Min-Seok, responded by saying 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."

Last month, South and North Korea exchanged fire at the tense border twice.

The two sides remain technically at war as they never signed a peace treaty at the end of the 1950-53 Korean War.

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