North Korea fired two warning missiles and swore "merciless" retaliation on Monday as the U.S. and South Korea readied to begin joint military drills.

The two North Korean missiles have a range of 310 miles, explained the South Korean military, according to the U.K.'s The Telegraph. The missiles were fired from Nampo, a western port city, and crossed the peninsula before hitting the ocean off the east coast.

The U.S.-South Korea joint military drills occur every year, and every year, Pyongyang amps up its rhetoric. According to The Telegraph, analysts view the missile tests as the beginning of more flexing of military muscle. Missile launches are North Korea's preferred form of showing displeasure with what the north believes is confrontational behavior from the south.

"And if there is a particularly sharp escalation, we could see the North orchestrating some kind of clash on the maritime border," said Jeung Young-Tae, an analyst at the Korea Institute for National Unification in Seoul, according to The Telegraph.

"The situation on the Korean peninsula is again inching close to the brink of a war," a spokesman for the North Korean People's Army (KPA) General Staff told the North's official KCNA news agency on Monday, according to The Telegraph. "The only means to cope with the aggression and war by the U.S. imperialists and their followers is neither dialogue nor peace. They should be dealt with only by merciless strikes."

According to The Telegraph, the Joint Chiefs of Staff said in a statement that it remained "vigilant against any launches."

Threats against the United States from North Korea have been launched before, but North Korea has not shown that it has missiles capable of reaching the U.S. mainland, according to The Telegraph.

As HNGN reported earlier, Foal Eagle - an eight-week military drill - began on Monday. The drills, which South Korea and the United States claim are defensive (not offensive), involve air, ground and naval training with 200,000 troops from South Korea and 3,700 U.S. troops. A second drill, Key Resolve, is mainly computer-simulated.