North Korean leader Kim Jong-Un has carried out a rash of visits to military installations and chaired a meeting of senior figures in the armed forces, state media said Sunday, amid global unease over a possible nuclear test.

The announcement by the Korean Central News Agency (KCNA) comes the day after US President Barack Obama lambasted the North as a "pariah" and said any atomic blast would lead to "more isolation".

After a series of visits to observe army drills over the last few days, Kim presided over an enlarged meeting of the Central Military Commission (CMC) of the ruling Workers' Party, KCNA said.

The meeting discussed ways to "win victory... in the confrontation with the US" as well as "organizational matters", the report said, suggesting a potential personnel reshuffle.

On Saturday, the agency said Kim had chided soldiers, telling them to be ready for "impending conflict with the United States".

Sunday's dispatch said Kim had led long-range artillery drills by the army unit "tasked to hit major targets" near the tense Yellow Sea border.

The young leader, who is supreme commander of the North's 1.2-million-strong armed forces, gave his seal of approval to the exercise, saying "All the shells... accurately hit their targets", according to KCNA.

The western sea boundary has been the scene of several bloody naval clashes in the past. Last month the two Koreas traded hundreds of shells across the border. There were no injuries on either side.

Kim's flurry of military activity came as the world was watching for signs Pyongyang was readying to carry out another atomic test.

The underground detonation could come "anytime," South Korean President Park Geun-Hye said Friday, after similar warnings by her own armed forces and from US nuclear experts.

Analysis of satellite images taken over the past week -- most recently on Friday -- showed increased activity at Punggye-ri, the site of the North's three previous nuclear tests in 2006, 2009 and 2013.

Pyongyang last month said it would not rule out a "new form" of nuclear test after the UN Security Council condemned its latest medium-range missile launches.

Experts saw this as a possible reference to testing a uranium-based device or a miniaturised warhead small enough to fit on a ballistic missile.

Obama, in Seoul this week as part of a four-nation tour of Asia, warned Pyongyang he would hit it with sanctions that have "more bite" if it went ahead with an atomic test.