South Korea's military fired warning shots after several North Korean soldiers crossed the border on June 20 morning, Seoul's Joint Chiefs of Staff (JCS) said, Report informs via Reuters.
The North Korean soldiers retreated after the warning shots were fired, the JCS added.
They had breached the Military Demarcation Line running through the middle of the Demilitarised Zone (DMZ) around 11 a.m. (0200 GMT) on Thursday.
It is at least the third such incident this month. South Korea's military fired warning shots on Tuesday after dozens of North Korean soldiers breached the demarcation line.
Although deadly clashes have occasionally occurred over the decades since open fighting between the countries stopped at the end of the 1950-1953 Korean War, the recent incidents mark a rare uptick in activity close to the demarcation line.
The incident came after Russian President Vladimir Putin visited Pyongyang for the first time in 24 years this week.
Kim Yo Jong, the powerful sister of the North's leader, separately issued a statement denouncing South Korean activists who late on Thursday flew balloons carrying leaflets toward the North, saying they will soon be criticized by their own people.