The South Korean military has begun a defense exercise near the five northwestern border islands in the Yellow Sea in the wake of North Korea's announcement on the launch of its first military spy satellite next month.

The three-day drills led by the Northwest Islands Defense Command involving the Army, the Navy, the Air Force and the Marines began on Tuesday around the islands of Baengnyeong, Yeonpyeong, Daecheong, Socheong, and Udo.

It is the first time in six years that the command has resumed the formerly biannual combined training.

According to military officials, the drills will cover various scenarios amid the North's evolving security threats, while the military has reinforced its readiness posture.

Seoul and Washington have reportedly mobilized the former's RC-800 and RF-16 reconnaissance planes, the latter's U-2S high-altitude strategic recon aircraft and RC-12X special electronic mission aircraft to monitor developments in the regime.