The U.S and South Korea have begun annual military drills Monday, amid rising tensions in the region as the North Korea escalated its war rhetoric in response to the drills and the recent U.N. sanctions against it.     

The annual military exercise named "Key Resolve" comes days after the U.N. Security Council passed new sanctions against the North Korea for conducting the third nuclear test in defiance to the U.N. regulations.

The North, furious over the sanctions and the U.S.-South Korea joint military drills had threatened to launch nuclear strikes against the allies and scrap the 1953 Armistice Agreement that ended the 1950-53 Korean War.

Pyongyang which considers the military drills as an invasion into their territory had also said it would snap the hotline Mar. 11, if Washington and Seoul do not abandon the annual exercise.

The analysts believe that although Pyongyang is working towards building a nuclear weapon small enough to mount a missile, it is not technically capable of doing it yet.

However, officials from Seoul said the North apparently has carried out the threat to cut-off the Red Cross hotline with the South, Monday.

"We called at 9 a.m. and there was no response," a government official from South Korea told Reuters. The line is tested each day.

The hotline is used to communicate between the rival countries as they do not have diplomatic relations. Pyongyang also has threatened to cut-off another hotline that is used to communicate with the U.N. base in South Korea.

The massive two-week long computer-simulated military exercises will last till Mar. 21, would see the participation of 10,000 Korean forces and 3,500 American personnel.

This year’s military drill is considered to be important as for the first time the South Korean forces were taking in a lead role in planning and executing the combat drills, as they prepare to regain their wartime operational control (OPCON) from Washington at the end of 2015.

"This year is particularly important, because it is the first time the ROK Joint Chiefs of Staff have planned and executed this combined exercise," Gen. James Thurman, Combined Forces Command commander said according to the South’s official news agency, Yonhap News.  “In doing so, they are taking great strides to assume wartime operational control of forces in December 2015."   

Meanwhile, reports from the South Korea state that the North is preparing to carry out massive unprecedented military drills at its eastern province this week in the wake of the U.S.-South Korea drills.

"The North Korean military is believed to have intensified military training in light of key resolve," ministry spokesman Kim Min-seok said in a briefing. "Currently, no special activities are observed in the North," the Yonhap News reported.

The Korean Peninsula remained tense as observers believe any provocation from either side during the military exercises could inflame the situation with disastrous consequences. The North has set no-fly and no-sail zones on its east and west coast indicating that they may fire short range missiles during the drills, if the zones are violated by the allies.  

Political observers point out that any accident during the drills could result in a flare-up that could lead to a confrontation between the rival forces.

The North’s February nuclear test and successful launch of a missile along with fiery-worded threats to launch nuclear strikes against Seoul have heightened the fears in the South of a possible attack on them.

The South Korean leaders normally react with restraint to the North’s threats, but recent coverage and comments from the South’s media and politicians point toward rising intolerance against the North, among South Koreans, the New York Times reported.

Breaking the normal approach of silence, the South Korean leaders have started responding to the North’s threat in a strong language. The country’s new President Park Geun-hye, who is just two-weeks-old in office vowed to respond strongly if her country is attacked. 

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