SEOUL (AFP) - North Korean leader Kim Jong Un has declared himself free from "all cares and worries" after inspecting a city inundated by flash floods that killed 40 people and damaged thousands of homes.

State media reported on Friday (Sept 18) that Kim had undertaken a tour of Rason after suffering sleepless nights worrying about the residents of the north-east special economic zone where the borders of North Korea, Russia and China converge.

"He could feel relieved only after looking round the scenes of recovery," the North's official KCNA news agency reported.

"I feel freed from all cares and worries," Kim was quoted as saying after inspecting the temporary and new housing being constructed for those left homeless by last month's floods.

KCNA did not specify the date of the visit.

While the news agency devoted much of its report to Kim's state of mind, it offered scant detail of the actual impact of the flooding.

It reported repairs to the houses of "thousands" of families and the temporary restoration of power, telecommunications and railway networks.

According to the International Federation of the Red Cross, the floods - triggered by torrential rains whipped up by Typhoon Goni - killed 40 people, and affected 11,000 others.

Decades of deforestation have left North Korea extremely vulnerable to floods.

During his visit, Kim urged those leading the recovery effort to wrap up their work before the 70th anniversary of the founding of the ruling Workers' Party on Oct 10.

Pyongyang is planning a massive military parade for the anniversary and has been banging its nationalist drums even louder than usual in the run-up to the event.

It has also hinted at a satellite rocket launch, despite warnings from the US and others that any such move would be seen as a disguised ballistic missile test and trigger fresh sanctions.