South Korea's Navy carried out maritime drills in the tensely guarded western sea on Monday ahead of the third anniversary of the sinking of the Cheonan warship by North Korea, amid high tensions with the communist country that has issued repeated threats of war.

The 1,200-ton Navy corvette with 104 personnel aboard sank in waters of Baengnyeong Island in Yellow Sea on March 26, 2010, killing 46 sailors. A multinational investigation team concluded that a North Korean torpedo was responsible for the sinking, but Pyongyang has denied its involvement.

The naval drill, which involved combat corvettes and missile patrol ships, occurred during a time of escalating tensions on the Korean Peninsula, with multiple threats from the North of an armed response to joint South Korea-U.S. military drills and to U.N. sanctions imposed after its nuclear test last month.

The anniversary drill was held separately from an ongoing South Korea-U.S. annual exercise, called Foal Eagle, which is being held from March 1 to April 30 to test the combat readiness of the allies' militaries.

The North also shelled the border island of Yeonpyeong in November 2010, an attack that killed two marines and two civilians and sent inter-Korean relations to one of its lowest levels in decades. The two countries still remain at war.

The Navy's chief visited the gravesites of the 46 soldiers who died in the attack and the servicemen who died in two deadly maritime skirmishes with North Korea near the border island in 1999 and 2002.

"Our military should strongly retaliate until the enemy surrenders if it provokes. This is what people want from the military and how we can pay tribute to our fallen soldiers," Adm. Choi Yoon-hee told soldiers during a visit to the national cemetery in Daejeon, 164 kilometers south of Seoul.

On Monday, Defense Minister Kim Kwan-jin visited military units on Baengnyeong Island to urge them to stay on high alert against North Korean provocations and assure residents on the westernmost site of their safety.

"Tomorrow is the third anniversary of the Cheonan sinking. We have to thoroughly prepare so as not to allow such unprovoked attacks (on the South) again," Kim told soldiers. "If (the North) provokes again, we have to strongly retaliate to prevent them from even thinking about attacks in the future."

Kim brought attention to North Korean leader Kim Jong-un's frequent military inspections, saying his latest move could be a sign of unprovoked attacks on the South.

"(Kim Jong-un's) front-line military inspections are aimed at creating a war-like situation," Kim said. "It could stir conflicts in the South and result in a real provocation. You have to be fully prepared for that."

Gen. Sung Il-hwan, Air Force Chief of Staff, also visited a fighter wing and a missile radar station in the central region, which operates ground-based Israeli-made Green Pine radars, and told soldiers to keep in mind the sacrifices made by their fallen soldiers.

Two Green Pine radars were deployed at the end of last year to track North Korea's ballistic missiles.

Tensions on the peninsula remain high as North Korean leader Kim Jong-un has made frequent visits to military units and front-line artillery troops urging soldiers to stay on high alert to prepare for an all-out battle with the South.

Following the two deadly attacks, Seoul has repeatedly pledged to retaliate against the communist country with greater force if provoked again.

In response to the escalating risk of North Korean provocations via sea route, South Korea has upgraded its defense capacities along the Yellow Sea border, with advanced torpedo countermeasures as well as additional aircrafts that can deal with anti-submarine and surface threats.

While the Navy has stepped up its anti-submarine capability, R. Adm. Yoon Jung-sang, who oversees the Navy's weapons program, called for the need to further increase vessels and maritime aircrafts to carry out underwater surveillance and anti-submarine operations against the North, which has a large fleet of submarines.

The latest move comes as the North is now showing signs it may be ready to provoke the South once again.

According to South Korean military officials, the North has recently increased operations of its submarine fleets and training of coastal artillery units, and may have even beefed up secret infiltration missions targeting the South.

Since last year, the North Korean military has intensified amphibious training involving ground, naval and air force elements, and focused on tactics to attack the group of South Korean border islands lying along the maritime border.

(Yonhap News)