North Korea fired two short-range missiles into the East Sea on Monday in an apparent saber-rattling against annual military drills between South Korea and the United States, the Joint Chiefs of Staff said.

Seoul and Washington kicked off their joint annual Key Resolve and Foal Eagle military exercises earlier in the day as part of efforts to improve the combined forces' operation and combat capabilities to deter threats from the communist country.

"North Korea fired two short-range missiles with a range of some 490 kilometers into the East Sea from its western port city of Nampo between 6:32 a.m. and 6:41 a.m. today," the JCS said in a short release.

Factoring in its range, the missiles are presumed to be Scud-C or Scud-D type ones, according to JCS officers, adding they appear to have landed in the East Sea after flying across its inland areas.

Monday's firing is the North's third missile launch this year.

Last month, the bellicose regime fired five short-range missiles into the East Sea from its eastern border town of Wonsan just two days after the launch of anti-ship missiles under the guidance of leader Kim Jong-un, according to the JCS.

Noting that the firing "appears to be the North's provocations in opposition to the Key Resolve and Foal Eagle exercises," the JCS said it "remains vigilant against any additional launches while strengthening the readiness posture."  

North Korea has long called on the two countries to stop the military exercises and vowed to retaliate, claiming that the drills are "a dress rehearsal for a northward invasion."

Earlier in the day, an unidentified spokesman for the General Staff of the (North) Korean People's Army issued a statement and vowed "merciless strikes."

"Key Resolve and Foal Eagle are an undisguised encroachment upon the sovereignty and dignity of the DPRK and an unpardonable war hysteria of dishonest hostile forces," said the statement carried by the North's state media Korean Central News Agency (KCNA) monitored in Seoul.

"The only means to cope with the aggression and war ... is neither dialogue nor peace. They should be dealt with only by merciless strikes," the North said, warning that the U.S. and South Korea "will have to bitterly regret the irretrievable consequences to be entailed by Key Resolve and Foal Eagle."

The two-week war game Key Resolve mobilizes about 10,000 South Korean and 8,600 American troops to test various scenarios in which South Korea's Joint Chiefs of Staff plays a leading role in conducting operations, while the field training exercise Foal Eagle involves a set of land, sea and air maneuvers, from March 2 to April 24 by 200,000 Korean and 3,700 American troops.

The large-scale annual drills are expected to further heighten tensions on the Korean Peninsula, with Pyongyang issuing near-daily threats of harsh retaliation of "hostile" forces.

Despite Pyongyang's demand, South Korea and the U.S. have said they will go ahead with the plan, as the regular exercises are defensive in nature and aim solely to bolster readiness against a possible invasion by the communist North. (Yonhap)