An aircraft used by North Korean leader Kim Jong-un flew from Pyongyang to the eastern part of the country on Wednesday, an aviation tracker said, sparking speculation that the leader may reemerge into public view for possible military action amid heightened inter-Korean tensions.

The An-148 twin-engine jet was spotted flying northeastwards at around 10:00 a.m. Wednesday, Aircraft Spot said. It said the plane's signals disappeared near North Hamkyong Province.

North Korea watchers have said that the Air Koryo plane has been used as Kim's personal aircraft in the past.

"The An-148 would be good for a short hop," a tracker operator told Yonhap News Agency, noting that Kim's other plane, IL-62, is made for longer-range trips though both are "configured to his luxurious needs."

"Honestly it's hard to tell who is aboard what plane, and when. But I did see that his An-148 flew in a north-easterly direction away from the region where his palace is," the operator said.

The rare movement of Kim's personal plane comes after North Korea warned of military action against South Korea in protest over activists' anti-regime leafleting across the border.

While his powerful sister, Kim Yo-jong, has issued a series of blistering statements against the South, the leader has been absent from public view for more than a week.

Given the flight direction, some say its destination might have been Sinpo on the east coast, where North Korea is believed to have been building a new submarine. It is estimated to be in the final stage of construction.

The new submarine is believed to be a 3,000-ton class vessel and may be capable of carrying three submarine-launched ballistic missiles (SLBMs). (Yonhap)