The balloon briefly entered South Korean airspace yesterday, the ministry of defence said in a statement, adding it in response had taken unspecified “measures”.

The craft left South Korean airspace a few hours later and officials believe it was a weather balloon not one intended for spying activities, Yonhap news agency reported, citing an unnamed official.

The report comes after the US shot down a suspected Chinese surveillance balloon, further straining relations with Beijing which said the craft was a civilian airship that had accidentally strayed into US airspace.

Tensions have risen between the two Koreas, with the North conducting a record number of missile tests last year, and the South joining with US allies in military shows of force.

Five North Korean drones crossed into the South on Dec 26, including one that briefly entered a no-fly zone surrounding South Korea’s presidential office, prompting South Korea’s military to scramble fighter jets and helicopters.

The military were criticised for failing to bring down the drones, which flew over the South for hours.