South Korea is set to stage large- scale drills Thursday involving fighter jets and artillery guns near a heavily fortified land border with the Democratic People's Republic of Korea (DPRK) amid lingering military tension.

The joint drills between the Army and the Air Force at a firing range in Pocheon, 40 kilometers northeast of Seoul and 25 kilometers south of the mainland border, will be part of regular exercises yet the largest one of its kind.

The exercises, aimed at testing fire power, will mobilize some 800 soldiers along with missiles, fighter jets and helicopters, according to officials.

The latest show of force by South Korean forces coincides with three-day drills in waters off the east coast of the Korean peninsula that started Wednesday, which involves navy vessels and Lynx anti-submarine helicopters.

The drills follow a high-profile live-fire exercise Monday from the western border island of Yeonpyeong, shelled last month by the DPRK in what Seoul believes was an unprovoked attack.

The DPRK repeatedly vowed retaliation against the firing drill near a sea border it refuses to acknowledge, but did not immediately respond to it.

Though saved from an immediate clash, South Korean forces remain vigilant against retaliation from the DPRK, deploying an Aegis destroyer and putting fighter jets on standby.

Concerns are rising that a Christmas tree on the top of the Aegibong hill in the South Korean city of Gimpo, lit up earlier this week, might be a potential target of the DPRK's strike for being a perceived anti-Pyongyang propaganda tool.

The annual ritual of lighting up the symbolic tree was suspended in 2003 as the two Koreas, amid a conciliatory mood, agreed to stop propaganda war.