The South Korean military says North Korea has blown up sections of inter-Korean roads on its side of the border.

South Korea's Joint Chiefs of Staff said the North carried out the explosions at around noon on Tuesday. It said the blasts occurred on roads in the eastern and western areas of the Korean Peninsula. The damaged sections are on the northern side of the military demarcation line.

No damage or casualties have been reported by the South Korean military.

The military said it fired warning shots on the southern side of the border as the North was continuing related work following the explosions.

Last Wednesday, the North's Korean People's Army said that permanently blocking the border with South Korea is a self-defense measure to deter war and protect the country. It announced plans to sever roads and railways between the two countries and to fortify the area with defensive structures.

The South Korean military said on Monday that the North was preparing to blow up roads. It added that it had since boosted surveillance of the North.

It is stepping up vigilance of the North's actions in coordination with the US forces.