North Korea shoots fireworks during a ceremony for the 112th birthday of late national founder Kim Il-sung in Pyongyang, April 14. Yonhap

The unification ministry said Tuesday that North Korea is believed to have changed the official name of the birthday of late national founder Kim Il-sung to just "4·15" from the Day of the Sun.

Kim's birthday, April 15, has been revered as the Day of the Sun in North Korea since 1997 and celebrated as one of the country's most important national holidays, along with the birthday of his late son and successor Kim Jong-il in February. The senior Kim died of heart failure in 1994 at age 82.

But since Feb. 18, North Korean state media has referred to Kim's 112th birthday as "the April holiday" or "the spring holiday in April," spawning speculation that Pyongyang is viewing his birthday as less important than before.

On Monday, the Day of the Sun reference reemerged in the Rodong Sinmun, the North's main newspaper, but only in one article, and there was no such report in Tuesday's edition.

"North Korea's state media have called his birthday '4·15' or 'the April holiday.' Compared with past cases, the country seems to have intentionally replaced or removed the term Day of the Sun," a ministry official told reporters on condition of anonymity.

The official said the North's incumbent leader Kim Jong-un may seek to refrain from excessively extolling his late grandfather in a possible move to focus the country's personality cult on himself. Kim Il-sung is long known as the role model of Kim Jong-un.

But at a year-end party meeting, Kim Jong-un scrapped a decadeslong policy of seeking unification with South Korea, a legacy of his grandfather, and defined inter-Korean ties as those between "two states hostile to each other."

In January, the North's leader ordered the dismantling of a monument in Pyongyang built to mark Kim Il-sung's blueprint for a federation system-based unification, describing it as an "eyesore." (Yonhap)