The tests come a day after North Korea called an American movie involving an assassination attempt on its leader, Kim Jong Un, an "act of war." The missiles took off from the coastal town of Wonsan and flew 118 miles before landing in the water between Japan and North Korea, according to a spokesman at the Ministry of National Defense in South Korea.
"We are analyzing our data to try to figure out what type of projectiles they were and why the North fired them," the spokesman told the New York Times, speaking on the condition of anonymity. "Our military has increased its monitoring activities in case the North should fire more projectiles."
"The 300-millimeter launcher is known to have an up to 160 kilometer range," said a South Korean official with the country's Joint Chiefs of Staff. "As of now, it is yet to be confirmed if the North enhanced its capacity."
North Korea has been known to launch such missiles during military exercises or when it wants to raise tensions in the region. It remains unclear if these launches were linked to North Korea's threat of retaliation if the movie, called The Interview, was not banned by the U.S. government.
The movie's plot involves a talk show host and his producer visiting North Korea for an interview with Kim Jong Un, but instead planning to assassinate him with the help of the Central Intelligence Agency.
North Korea test-fired missiles in a similar exercise three months ago, launching 30 short-range rockets off its east coast.