A US civil aviation tracking website over South Korea said yesterday that a surveillance plane was launched over South Korea, the latest in a series of almost daily launches of aircraft to monitor North Korea, amid speculation about the health of North Korea's leader, Kim Jong Un , According to South Korean Yonhap News Agency yesterday.

The Aircraft Spot website added, in a tweet, that the US Air Force's R-C-135W Revit Joint plane was detected in the sky over Seoul and the neighboring Gyeonggi Province, without specifying the time of the operation.

This type of aircraft was last detected on Monday, which came in the wake of observations by the Air Force E-8C and the navy B-3C, according to the website.

The United States has allowed several spy planes to be launched over the Korean peninsula more than in recent months, after Pyongyang has sought to boost its defense capabilities amid disrupted disarmament talks with Washington.

On the other hand, North Korea ignored reports about the health of North Korean leader Kim Jong-un yesterday, after US media reports said he was in critical condition.

American media reported yesterday that Jong Un, who is believed to be 36, is not in good condition after undergoing a heart operation and is currently receiving treatment.

Yesterday, the North Korean media did not mention the location of the North Korean leader or his latest public appearance.