South Korea is analyzing whether projectiles North Korea fired into its eastern waters over the weekend are short-range missiles or a new type of artillery the country may be developing, officials said Monday.

North Korea fired what Seoul officials called a short-range projectile Sunday, a day after conducting three similar launches. South Korean officials earlier said the weapons fired on Saturday were guided missiles but later clarified that they may not be missiles, referring to the objects as "projectiles."

"There is a possibility that they are short-range missiles or large-caliber rockets with a similar ballistic trajectory," Defense Ministry spokesman Kim Min-seok told reporters.

Kim said North Korea may be developing such a large-caliber gun and South Korea is taking seriously whatever weapons the country develops because it could attack the South. He said an artillery gun with a bigger caliber will likely have more destructive power.

Officials were trying to find out what exactly the North fired Saturday and Sunday, a ministry official said on condition of anonymity citing department rules.

North Korea routinely test-launches short-range missiles. But the latest launches came amid some tentative signs of easing tension on the Korean Peninsula. Earlier this year, North Korea issued near-daily threats to attack South Korea and the U.S. to protest their annual joint military drills and U.N. sanctions imposed over its February nuclear test.

South Korea called the latest launches a provocation and urged the North to take responsible actions while the U.S. said threats or provocations would only further deepen North Korea's international isolation, while

The North has a variety of missiles but Seoul and Washington don't believe the country has mastered the technology needed to manufacture nuclear warheads that are small and light enough to be placed on a missile capable of reaching the U.S.

The Korean Peninsula officially remains in a state of war because the 1950-53 Korean War ended with an armistice, not a peace treaty.