Japan's government warned Wednesday against "escalation" on the Korean peninsula, after North Korea blew up sections of deeply symbolic roads and railways connecting it to the South.

"These North Korean activities could increase tensions between the South and the North, and it is important that this does not lead to an escalation," said Kazuhiko Aoki, deputy chief cabinet secretary.

The North blew up the roads and railways on Tuesday, Seoul's military said, adding it had conducted a "counter-fire" operation in response.

Pyongyang's military last week vowed to permanently seal its southern border after spending months laying mines and building anti-tank barriers in the wake of leader Kim Jong Un declaring the South his country's "principal enemy".

The North also accused Seoul of using drones to drop anti-regime propaganda leaflets on the capital Pyongyang, with Kim convening a security meeting to direct a plan of "immediate military action" in response, state media reported Tuesday.

"The government will do its utmost to collect, analyse and monitor necessary information on future developments in North Korea," Aoki told a regular briefing in Tokyo.