Passengers get on board a ferry to Yeonpyeong Island at Incheon Port, May 30. Fishing boats and passenger ships in the area suffered glitches in their navigation system due to North Korea's GPS jamming attacks. Yonhap

North Korea attempted to jam GPS signals for a second straight day Thursday, the South Korean military said, a day after the North sent hundreds of balloons carrying waste and manure to the South.

The military detected the GPS jamming attacks from 7:50 a.m. near the de-facto inter-Korean sea border in the West Sea, according to the Joint Chiefs of Staff (JCS). North Korea also attempted to jam GPS signals early Wednesday.

The jamming attacks, which have ceased, did not hinder any military operations, a JCS official said.

But fishing boats and passenger ships in the area suffered glitches in their navigation systems, with 472 complaints related to GPS signals filed in the area between 5:50 a.m. Wednesday and 9 a.m. Thursday, according to the National Maritime Positioning, Navigation and Timing Office in charge of providing positioning information.

North Korea sent hundreds of balloons carrying trash and fecal matter to the South on Tuesday and Wednesday after it vowed to scatter "mounds of wastepaper and filth" over the inter-Korean border areas in retaliation against anti-Pyongyang leaflets sent by activists in South Korea.

An ongoing analysis of some 260 balloons detected by the military showed that each balloon carried bags weighing 10 kilograms on average that contained cigarette butts, pieces of fabric, batteries and manure, according to the JCS.

No propaganda leaflets or chemical, biological and radiological contaminants have so far been found during the analysis under way, it added.

The military once again condemned the launch of balloons and warned the North against carrying out additional provocations.

"All responsibility in relation to the filth balloons lies with North Korea," JCS spokesperson Col. Lee Sung-jun said in a regular press briefing. "We once again sternly warn North Korea to immediately cease its vulgar and shameful act that violates the Armistice Agreement and goes against humanity."

Instead of shooting down the balloons, the military opted to remove them once they have safely fallen to the ground to prevent possible toxic substances spreading and fired artillery rounds from going over to the North, Lee added.

For years, North Korean defectors in South Korea and conservative activists have flown the leaflets to the North via balloons to help encourage North Koreans to eventually rise up against the Pyongyang regime.

North Korea has bristled at the propaganda campaign amid concern that an influx of outside information could pose a threat to its leader Kim Jong-un.

North Korea has repeatedly called for an end to the leafleting campaign. The issue has long been a source of tension between the two Koreas, which are still technically at war because the 1950-53 Korean War ended in a truce, not a peace treaty. (Yonhap)