North Korea sent around 90 balloons carrying trash to South Korea on Saturday, Seoul's military said, after it launched hundreds of similar balloons across the inter-Korean border earlier this week.

As of 11 p.m., the Joint Chiefs of Staff said it had detected around 90 balloons that floated across the Military Demarcation Line separating the two Koreas and fell in Seoul and Gyeonggi Province.

The North appears to have started sending the balloons at around 8 p.m., with the fallen balloons carrying various pieces of trash, such as cigarette butts, paper and plastic bags, according to the JCS.

North Korea sent around 260 balloons carrying trash and excrement to the South on Tuesday and Wednesday, after it warned of "tit-for-tat action" against anti-Pyongyang leaflets sent by the South's activists.

The JCS advised people not to touch the objects and report them to nearby military or police authorities, and cautioned of possible damage from the balloons.

The Seoul city government also issued an emergency alert for safety, saying that unidentified objects presumed to be the North's balloons were detected over the sky near Seoul.

Kim Yo-jong, the powerful sister of North Korean leader Kim Jong-un, said Wednesday that the balloons were "sincere presents" for South Koreans who are crying for the guarantee for freedom of expression. She said her country will send rubbish "dozens of times" more than those being scattered in the North.

Seoul's unification ministry warned Friday it will take "unendurably" painful measures against North Korea if it continues to stage "irrational" provocative acts.

The government may consider staging psychological warfare against North Korea, including military authorities' resumption of loudspeaker broadcasting along the border or the sending of leaflets critical of the North's regime.

North Korea intensified its provocations this week following the botched attempt to launch a spy satellite Monday. The country staged GPS jamming attacks in waters near South Korea's northwestern border islands for the fourth straight day Saturday.

North Korea also fired a barrage of artillery from super-large multiple rocket launchers toward the East Sea on Thursday in a drill that it said was to demonstrate a resolve to conduct a preemptive strike against South Korea. (Yonhap)