The South Korean military said on Sunday it had detected the trajectories of what appeared to be North Korean fires, possibly from multiple launch rocket systems (MLRS), Reuters reported.

The South Korean Joint Headquarters said the shots were detected after 6:00 pm local time, and that the military had stepped up surveillance and alert levels.

North Korea has test fired a range of missiles this year, from its largest intercontinental ballistic missile (ICBM) to small IRBMs. All are banned by UN Security Council resolutions that have imposed sanctions on North Korean missile development.

South Korea is developing a $2.6 billion artillery interception system similar to Israel's Iron Dome system, designed to defend against North Korea's arsenal of long-range guns and missiles.

Much of the area around Seoul, the nation's capital, home to about half of the country's 52 million people, is within range of North Korea's long-range guns and multiple launch rocket systems.

The US has stationed about 28,500 troops in South Korea, where they train alongside South Korean troops to counter North Korea. The Allies conducted their own missile exercises in response to some of North Korea's earlier launches.