内容摘要：A ship departs from Incheon coastal passenger terminal in Incheon, May 30. (Yonhap)North Korea stage

A ship departs from Incheon coastal passenger terminal in Incheon, May 30. (Yonhap)

North Korea staged GPS jamming attacks in waters near South Korea's northwestern border islands for a third straight day on Friday, the South's military said, in the latest in a series of provocative acts this week.

The military detected the jamming signals from about 8 a.m. directed toward the islands near the Northern Limit Line in the West Sea, the de facto western maritime boundary between the two Koreas, according to a South Korean military official.

The latest attempt has not hindered the military's operations, the official said, although similar attempts the previous day led to glitches in the navigation systems of fishing boats and passenger ships in the waters.

The military detected the Thursday attack shortly after the North launched 18 rounds of multiple rocket launchers toward the East Sea.

The North's GPS jamming attempts this week first took place Wednesday as it was sending hundreds of balloons carrying trash and apparent fecal matter to the South after it vowed to scatter "mounds of wastepaper and filth" in retaliation against anti-Pyongyang leaflets sent by activists in the South.

Another military official said the North could send more of such unpowered balloons Saturday when the wind is forecast to blow in a southward direction, although the military has yet to detect preparations of such launches.

A person cleans up a balloon presumably sent by North Korea in Pyeongtaek, Gyeonggi Province, May 29. Yonhap

On Wednesday night, Kim Yo-jong, the powerful sister of the North's leader, called the balloons "sincere presents" and said her country will send rubbish "dozens of times" more than those being scattered in the North.

"We are closely monitoring the North Korean military's activities," the South Korean official told reporters. "If the filth balloons are flown, we plan to notify the media."

The official advised the public not to touch such balloons that have fallen and report them to the authorities.

The military has decided against shooting down the balloons, the official said, noting that collecting them when they have fallen is currently the safest and most efficient way to respond to them.

"We are considering necessary measures, and are prepared and have the capabilities for stronger action," the official said, without elaborating.

The North's series of provocative moves came after its botched attempt to launch its second military spy satellite into orbit Monday night. The launch failed as the rocket exploded shortly after liftoff. (Yonhap)