POCHEON, South Korea - The Republic of Korea (ROK) mobilized troops, tanks, helicopters and fighter jets Thursday for its largest air and ground drills this year

The drills, set to take place at training grounds in mountainous Pocheon near the two countries' heavily fortified border, signaled ROK's determination to demonstrate and hone its military strength at the risk of further escalation with the Democratic People's Republic of Korea (DPRK).

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A helicopter hovered overhead and military music played over the loudspeakers as troops geared up for the drills. A thick fog hung over the area, which lies about 20 miles (30 kilometers) from the North Korean border in an area dotted with ski resorts.

Exactly one month ago, routine ROK live-fire drills from Yeonpyeong Island in the Yellow Sea triggered a shower of DPRK artillery that killed two marines and two construction workers. It was the first military attack on a civilian area since the 1950-53 Korean War ended in a truce.

The DPRK, which claims the waters around the ROK-held island lying just 7 miles (11 kilometers) from its shores as its territory, accused ROK of sparking the exchange by ignoring Pyongyang's warnings against staging the live-fire drills near their disputed maritime border.

Amid international concerns of all-out war on the tense Korean peninsula, the ROK has pushed ahead with military exercises over the past several weeks, including live-fire drills from Yeonpyeong Island and Monday's land-based exercises.

Thursday's drills will be the largest-scale firing exercise jointly staged by ROK's army and air force this year, and the biggest-ever wintertime air and ground firing exercises, government and army officials said on condition of anonymity citing department rules.

Forty-seven similar exercises have taken place this year but Thursday's maneuvers were scheduled in response to the DPRK attack, according to army officials.

"We will thoroughly punish the enemy if it provokes us again as with the shelling of Yeonpyeong Island," Brig. Gen. Ju Eun-sik, chief of the ROK army's 1st Armored Brigade, said in a statement Wednesday.

There was no immediate response from the DPRK, which has shown restraint in recent days.

The two countries remain technically at war because their 1950s conflict ended in a cease-fire, not a peace treaty.

The military tension over the past month has been the worst in more than a decade, and comes on the heels of the March sinking of a ROK warship that Seoul blames on Pyongyang, but which the DPRK denies attacking. Forty-six sailors died in that incident.

Thursday's drills are to include 30 K-1 tanks, 11 K-200 armored personnel carriers, two F-15K jets, four KF-16, 36 K-9 artillery pieces, three multiple long-range rockets, four 500MD helicopters, three AH-1S cobra helicopters, and other equipment and 800 troops, according to the army.

ROK's navy also was conducting annual anti-submarine exercises off the east coast.

In Pocheon, dozens of soldiers and civilians, including schoolchildren in bright yellow jackets, sat in bleachers on the side of a mountain overlooking the training grounds. As children finished the long walk up a steep road to get to the site, some cheered with relief.

Beneath the bleachers, tanks with brightly colored flags and jeeps lined up on a plateau overlooking a wide valley cut through with roads and paths where the drills were to take place.