A North Korean drone ventured into its neighbour's airspace for at least seven hours, South Korean media said, citing the military

The South Korean military has said it fired more than 100 rounds at a trespassing North Korean drone on Monday, but failed to down it, according to Yonhap news agency. It is estimated that several unmanned aerial vehicles (UAV) remained in the South Korean airspace for seven hours.

The South Korean Joint Chiefs of Staff were quoted by local media after warplanes were scrambled to intercept the UAVs and a military helicopter attempted to use its 20mm gun to take out a drone. The UAV had been spotted near Gyodong Island, to the northwest of Seoul and close to the North Korean border.

The military said it respected concerns that residential buildings could have been damaged, according to local media. The North Korean drones are said to have made evasive maneuvers in response to the attacks. 

In total, Yonhap cited the military as saying that it detected five North Korean drones, with one flying between the cities of Gimpo and Paju to Seoul's northwest, before going as far as the northern part of the South Korean capital. After that, the aircraft returned to North Korea.

The other four drones were active in the Ganghwa Island area, closer to the North Korean border. Their exact fate is unclear, since South Korean radar assets lost track of them. However, it is believed that Pyongyang's drones were inside South Korean airspace for seven hours.

Yang Moo-jin, a professor at the University of North Korean Studies, was quoted by the Hankyung news website as saying that "the main purpose of the UAV seems to be reconnaissance" on the South Korean side.

Meanwhile, Hong Min, head of the North Korea Research Department at the Institute for National Unification, told Yonhap news agency: "It seems that North Korea is responding to the US military's strengthened reconnaissance and surveillance flights... around Christmas."

The interception resulted in the crash of one South Korean aircraft, with both pilots surviving the incident. The operation also forced local officials to temporarily halt all civilian flights at Incheon and Gimpo international airports.

The drone incursion, which was denounced by Seoul as an "obvious provocation," came after last week's joint exercises involving US and South Korean warplanes. North Korea has repeatedly said it regards such drills as a preparation for an attack.