The US and South Korea are continuing their annual military exercise, south of the capital Seoul. US military officials say the drills are defensive, and are aimed at testing both countries' capabilities and coordination. The Democratic People's Republic of Korea has criticized the war games, saying it is on alert to respond to any provocation.

A show of force to deter aggression.

The US and South Korea brought out the heavy armor, tightening their alliance amid recent tensions on the Korean peninsula. .

The two countries are staging a military drill at Camp Carroll, in North Kyongsang Province, as part of the Key Resolve and Foal Eagle 2011.

The annual U.S.-South Korea exercises began on February 28 and is scheduled to run till the end of April.

The US army said the training is designed to test all phases of combat readiness, and the integration process.

The routine drills come at a sensitive time, raising the stakes in an already tense situation on the Korean peninsula.

Tensions have been high since 46 sailors were killed in an attack last March on a South Korean naval vessel.

The DPRK, which has denied responsibility for the naval attack, shelled the southern island of Yeonpyeong last November, killing four people.

On Sunday, the DPRK said it would respond to the military drills with an "all-out war" if there were any provocation.

KRT Newsreader, said, "As already declared, our army and people will deal a resolute and merciless blow to those who dare attempt to violate the dignity of the nation even in the least and overthrow our system."

Attempts at restarting talks broke down earlier in February, dealing a setback to resuming the stalled six party talks aimed at denuclearizing the Korean peninsula.

The DPRK says it wants to resume broader negotiations, but Seoul and Washington have questioned its sincerity about denuclearising.