Fidel Castro, the Cuban revolutionary leader, has warned longtime ally North Korea that it should not risk a war which could “affect more than 70 percent of the world’s population.”

In a rare written commentary piece in Cuban state media, Castro, 86, described the situation on the Korean peninsula as “incredible” and “absurd.”

Saying he was speaking as a friend, Castro wrote that Pyongyang — with Kim Jong Un at the helm — had shown the world its technical prowess and now it was time to remember its duties to others.

“If war breaks out there, the people of both parts of the peninsula will be terribly sacrificed, without benefit to all or either of them. Now that [North Korea] has demonstrated its technical and scientific achievements, we remind her of her duties to the countries which have been her great friends, and it would be unjust to forget that such a war would particularly affect more than 70 per cent of the population of the planet.”

He said North Korea’s declaration of war this week and threatened nuclear attack on the US constituted “one of the gravest risks of nuclear war” since the Cuban missile crisis, Reuters wrote.

Castro led Cuban during the 1962 crisis, when the US and Soviet Union nearly went to war over the placement of Soviet nuclear missiles on Cuba, 90 miles south of Florida.

The LA Times cited analysts as saying that North Korea was not capable of carrying out a nuclear strike, but that the escalating threats had raised tension and diverted global attention.

Castro also warned the US over its role in the crisis.

“If a conflict of that nature should break out there, the government of Barack Obama in his second mandate would be buried in a deluge of images which would present him as the most sinister character in the history of the United States. The duty of avoiding war is also his and that of the people of the United States.”