Image copyright Reuters Image caption North Korean leader Kim Jong-un has defied the international community by continuing to test missiles and nuclear weapons

A fresh nuclear test at North Korea's mountainous testing site could trigger a leak of radioactive material, South Korea's chief meteorologist has warned.

A hollow space of up to 100m in length in the bottom of Mount Mantap could implode, Nam Jae-cheol said.

Pyongyang's last nuclear test in early September appeared to have triggered several landslides.

North Korea has conducted six nuclear tests since 2006, using the same site test each time.

"There is a hollow space, which measures about 60 to 100 metres in length, at the bottom of Mount Mantap in the Punggye-ri site," Mr Nam was quoted by South Korean news agency Yonhap as saying.

"Should another nuke test occur, there is the possibility of a collapse," he warned.

The Punggye-ri test site, situated in mountainous terrain in the north-east of the country, is thought to be Pyongyang's main nuclear facility and the only active nuclear testing site in the world.

Image copyright Planet / 38 North Image caption A close-up of the Punggye-ri test site as photographed days before the September test

Hong Kong's South China Morning Post newspaper reported on Friday that Chinese geologists warned North Korean officials after the September test that additional tests there could lead to a massive collapse and a leak of radioactive waste.

Separately, North Korea's main newspaper, Rodong Sinmun, has said the country has a sovereign right to launch satellites.

The statement comes amid speculation that Pyongyang might soon launch a satellite - widely seen as a test of the country's ballistic missile technology.