South Korea and the United States have begun annual military drills despite North Korean threats to respond by voiding the armistice that ended the Korean War and launching a nuclear attack on the US.

After the start of the drills, South Korean officials said their northern counterparts didn’t answer two calls on a hotline between the sides, apparently following through on an earlier vow to cut the communication channel because of the drills. 

Pyongyang has launched a bombast-filled propaganda campaign against the drills, which involve 10,000 South Korean and about 3000 American troops, and last week’s UN vote to impose new sanctions over the North’s February 12 nuclear test.

Analysts believe that much of that campaign is meant to shore up loyalty among citizens and the military for North Korea’s young leader, Kim Jong Un. 

Pyongyang isn’t believed to be able to build a warhead small enough to mount on a long-range missile, and the North’s military has repeatedly vowed in the past to scrap the 1953 armistice.

North Korea wants a formal peace treaty, security guarantees and other concessions, as well as the removal of 28,500 US troops stationed in South Korea. 

Still, South Korean and US officials have been closely monitoring Pyongyang’s actions and parsing the torrent of recent rhetoric from the North, which has been more warlike than usual. 

North Korea regularly claims South Korea-US drills are a preparation for invasion, but Pyongyang has signalled more worry about the drills that began today.

The drills follow UN sanctions that the North said were the result of US hostility aimed at toppling its political system.

North Korea has also warned South Korea of a nuclear war on the divided peninsula and said it was cancelling nonaggression pacts.

Under newly inaugurated President Park Geun-hye, South Korea’s Defense Ministry, which often brushed off North Korean threats, has looked to send a message of strength in response to the latest threats.

The ministry warned Friday that the North’s government would ‘‘evaporate from the face of the Earth’’ if it ever used a nuclear weapon.

The White House also said the US was fully capable of defending itself against a North Korean ballistic attack.

North Korea has said the US mainland was within the range of its long-range missiles, and an army general told a Pyongyang rally last week that the military is ready to fire a long-range nuclear-armed missile to turn Washington into a ‘‘sea of fire’’.

While outside scientists were still trying to determine specifics, the North’s rocket test in December and third atomic bomb test last month may have pushed the country a step closer to acquiring the ability to hit the US with weapons of mass destruction.

Analysts, however, said Pyongyang was still years away from acquiring the smaller, lighter nuclear warheads needed for a credible nuclear missile programme. 

But there were still worries about a smaller conflict.

North Korea had a variety of missiles and other weapons capable of striking South Korea.

In 2010, North Korea shelled a South Korean island and allegedly torpedoed a South Korean warship, killing a total of 50 South Koreans.

Both incidents occurred near the disputed western sea boundary, a recurring flashpoint between the Koreas that has seen three other bloody naval skirmishes since 1999. 

Kim Jong Un visited two islands just north of the sea boundary last week and ordered troops there to open fire immediately if a single enemy shell was fired on North Korean waters. 

Kim was also quoted as saying his military was fully ready to fight an ‘‘all-out war’’ and that he would order a ‘‘just, great advance for national unification’’ if the enemy made even a slight provocation, according to the North’s official Korean Central News Agency.

Despite the threats, South Korea and the US began the 11-day war games as scheduled Monday.

The allies have repeatedly said the drills and other joint exercises were defensive in nature and they had no intention of attacking the North.

A US military statement said the exercise was not related to current events on the Korean Peninsula.

The drills were part of larger war games that began March 1 and were set to go on for two months. 

US troops in South Korea were meant to prevent North Korean aggression, US and South Korean officials said, and were a legacy of the Korean War, which ended with the peace treaty that left the Korean Peninsula still technically in a state of war.

- AP