This year's war games with the United States and South Korea are expected to last through the end of April. The maneuvers come as more stringent sanctions are readied for North Korea following nuclear and missile tests.
South Korean soldiers set up a camouflage net over a military tank during joint exercises with the US
The United States and South Korea began on Monday an expanded edition of their major annual military exercises in light of recent nuclear and missile launch tests by North Korea.
The North responded with threats of a "pre-emptive nuclear strike of justice" against the allied countries.
Both the war games and the North's bluster are annual occurrences, but tensions are higher this year. In response to the North's recent tests, the UN Security Council unanimously passed a new round of more stringent sanctions last week.
The sanctions target specific sectors of the North Korean economy, and include bans of all sales or transfers of small arms and light weapons to Pyongyang. They also impose mandatory inspections of cargo entering and exiting the communist country.
The resolution also empowers countries to expel North Korean diplomats who engage in "illicit activities." In a bid to target the country's elite, it also bans the sale of luxury items - including watches and even snowmobiles - worth more than $2,000 (1,825 euros).
The Philippines has already seized a North Korean cargo ship, which was among 31 listed by the resolution as banned from international ports.
North Korea slams sanctions
Pyongyang has rejected the sanctions as "unfair, illicit and immoral" and vowed to keep building its nuclear arsenal. The National Defense Commission's statement also threatened attack: "If we push the buttons to annihilate the enemies even right now, all bases of provocations will be reduced to seas in flames and ashes in a moment."
Given the heightened tensions, the US and South Korea expanded their annual military exercises, which this year involves 300,000 South Korean and 17,000 US troops.
The allied countries will work on drills for precision attacks on North Korean leadership and its nuclear and missile arsenal in the event of war, according to military sources. A pre-emptive large-scale military strike that would end the authoritarian rule of the Kim dynasty is highly unlikely.
Kim Jong Un is the third generation Kim to lead what is arguably the world's most isolated country. Kim inherited the mantle of Supreme Leader almost four years ago at the age of 29, after the death of his father Kim Jong Il - who succeeded his father Kim Il Sung.
South Korea said it will unveil new unilateral sanctions against the North on Tuesday.
The restrictions are expected to include an entry ban on any ships that have been to North Korea, and adding more North Koreans to its blacklist.
bik/msh (AP, AFP, dpa, Reuters)