South Korea has warned residents living near the border with North Korea to be on alert, after media reported that North Korea had sent balloons containing what appeared to be rubbish and faeces into its neighbour’s territory.

Report informs via The Guardian that photographs published in South Korean media showed an inflated white balloon with a plastic bag tethered to it. Another image showed what appeared to be a collapsed balloon with garbage strewn around it.

By Wednesday, more than 150 balloons had been detected, according to the Yonhap news agency. Some had landed on the ground, while others were still in the air, it added, citing a South Korean military source.

Some of the balloons had travelled long distances, reaching as far as the south-eastern province of South Gyeongsang, it said.

The fallen balloons appeared to have been carrying various items of rubbish, including plastic bottles, batteries, shoe parts and what is believed to be manure, an official of the joint chiefs of staff (JCS) said.

The military said unidentified objects believed to be from North Korea had been spotted near the demilitarised zone – the heavily fortified border separating the two Koreas. It urged people not to go near them and to report sightings to the military or police.