Takeoff and landing at South Korea's Incheon international airport was disrupted on Wednesday for about three hours before dawn because of balloons launched by North Korea filled with refuse, an airport spokesperson said.

One balloon landed on the tarmac near passenger Terminal 2 and the three runways at Incheon were temporarily shut down, the spokesperson said.

North Korea has flown balloons carrying trash into South Korea since late May, with hundreds landing in South Korea.

Several balloons were spotted in and around the airport boundaries, the spokesperson said, adding that this was not the first time operations at the airport – which is about 40km from the North Korean border – had been disrupted by balloons nearby.

The disruption to domestic and international flights occurred between 1.46am and 4.44am, and the runways have re-opened since then, Incheon International Airport Corporation said.

North Korea has said the balloons are retaliation for a propaganda campaign by North Korean defectors and activists in the South who regularly send over balloons carrying food, medicine, money and leaflets criticising the North's leaders.

Among the items carried by the North Korean balloons have been articles printed with Hello Kitty characters, badly worn clothing, and soil containing traces of human faeces and parasites, South Korea has said.

Meanwhile, North Korea test-fired what appeared to be a hypersonic missile off its east coast on Wednesday, but it exploded in midair, South Korea's military said.

The missile was launched from near the capital, Pyongyang, South Korea's Joint Chiefs of Staff said. Japan's Defence Ministry said the missile flew to an altitude of about 100km and range of more than 200km. (Reuters)