Kim Jong Un's sister warns of disaster if South Korean drones enter Pyongyang

North Korea's Kim Yo Jong, the powerful sister of leader Kim Jong un, on Saturday warned Seoul of a "horrible disaster" if South Korean drones are found flying over Pyongyang.

She also criticised the South Korean military over its response to the North's claim that South Korean drones entered the sky of the capital city in a statement carried by state media KCNA.

On Friday, North Korea's foreign ministry accused South Korea of sending drones into Pyongyang at night this week and last and that the intrusion demanded retaliatory action.

In response, South Korea's Joint Chiefs of Staff said it could not confirm the North's accusations.

"The fact that the means which carried the leaflets is the very drones is the core of the seriousness of the recent incident," Kim was quoted as saying, referring to anti-North Korea leaflets.

Kim said the blame lies with the South Korean military if it failed to identify drones sent by a non-governmental organisation crossing the border.

North Korea has been floating thousands of balloons with trash attached into the South since May, exacerbating tensions between the two countries.

Pyongyang says they are a response to some activists and North Korean defectors in South Korea who fly balloons into the North carrying aid parcels and leaflets criticising leader Kim Jong-un.