The youngest son of North Korean leader Kim Jong-Il has watched a military exercise along with his father, state media said Tuesday, his first such inspection since he was confirmed as heir apparent.

The report signalled a rapid rise to public prominence for Kim Jong-Un. The son's name and photograph had never appeared in official media until last week, when he was made a four-star general and given powerful ruling party posts.

The live-fire drill, also attended by top party and military officials, was staged ahead of a ruling party anniversary this Sunday, the Korean Central News Agency reported.

It did not say when or where the drill took place but referred to the younger Kim as vice-chairman of the party's central military commission, one of the posts he took last week.

"The troops powerfully displayed the power of the Korean People's Army that grew into invincible forces through training and under the guidance of General Kim Jong-Il," it said.

"This report shows to the outside world that Jong-Un has a firm position as heir apparent," Dongguk University professor Kim Yong-Hyun told AFP.

"By accompanying his father during field trips, the son is now being trained openly as successor. The drill also implies the son will inherit the father's army-first policy."

The North has a 1.2-million-member standing military whose welfare takes priority over civilians under the Songun (army-first) policy.

South Korean Defence Minister Kim Tae-Young predicted on Monday that the son would now begin public activities, as eventual successor to his ailing 68-year-old father.

The minister said the North appeared to be using the anniversary of the founding of the Workers' Party on October 10 to celebrate "the formation of a succession platform", and planned a major military parade and war games.

The leader-in-waiting of the impoverished but nuclear-armed nation remains a mystery to the outside world. The Swiss-educated Jong-Un, thought aged around 27, is not known to have held any formal posts before last week.

South Korea said it was closely monitoring work detected on satellite images at the North's Yongbyon nuclear reactor, the source of its weapons-grade plutonium.

Minister Kim said the North was restoring some facilities at the plant, closed in 2007 under a disarmament deal which Pyongyang angrily renounced in April 2009. A month later, it staged a second nuclear test.

Cross-border relations have been icy since the South accused the North of torpedoing one of its warships and killing 46 sailors in March, a charge it denies.

The South has warned of further possible provocations by the North as it puts its succession plan firmly in place and in the run-up to the G20 summit in Seoul in November.

The defence minister told parliament Tuesday the South would launch a full-scale propaganda war in response to any fresh provocation.

The South's military printed hundreds of thousands of leaflets and installed border loudspeakers as part of reprisals for the warship sinking.

Minister Kim said preparations were under way to float the leaflets and small radios by balloon across the tense and heavily fortified border.

"We will immediately switch loudspeakers on and launch leaflets" if there is a new provocation, or if a political decision is made to apply pressure on North Korea, he told legislators.

The North has threatened to open fire at the loudspeakers if they are switched on.

The minister also said that a North Korean jamming device capable of disrupting guided weapons poses a fresh threat to the South's security.

He said the North had imported Russian equipment to jam South Korea's Global Positioning System reception.

In one positive note, the two sides have agreed to resume reunions late this month for families separated by war 60 years ago.

earlier related report
N.Korea restores facilities at nuclear reactor: S.Korea
Seoul (AFP) Oct 5, 2010 - North Korea is restoring facilities at its Yongbyon nuclear reactor, the source of weapons-grade plutonium in the past, South Korea's defence ministry said Tuesday.

"North Korea is restoring nuclear facilities and continuing maintenance activities at Yongbyon," a spokesman quoted Defence Minister Kim Tae-Young as telling parliament on Monday. "It is engaged in new construction and large-scale excavation."

The foreign ministry said the South is closely monitoring the work.

"There are some activities going on but we have no information on what these are for," said spokesman Kim Young-Sun. "The government is watching closely the activities there and exchanging information with other countries."

An unidentified government official was quoted by Dong-A Ilbo newspaper as saying that two rectangular buildings were being built next to the site of a cooling tower demolished in 2008.

A private US research institute reported last week that new construction or excavation was under way at Yongbyon.

The Institute for Science and International Security (ISIS) said tracks made by heavy machinery along with construction or excavation equipment were visible in satellite photos.

ISIS said there appeared to be ongoing construction of two small buildings next to the former tower, which the North blew up in June 2008 in front of foreign media to dramatise its commitment to nuclear disarmament.

The institute said the purpose of the work is unclear but bears watching.

The North's current plutonium stockpile is believed to be enough for six to eight bombs.

North Korean Vice Foreign Minister Pak Kil-Yon told the United Nations last week his country must strengthen its nuclear deterrent in the face of what he called threats from the United States.

The North shut down Yongbyon in July 2007 under a six-nation aid-for-disarmament accord. The following summer it destroyed the tower.

But six-party talks became bogged down in December 2008 over ways to verify the North's denuclearisation. In April 2009 Pyongyang abandoned the talks and said it had resumed reprocessing spent fuel rods to make plutonium.

In May 2009 it conducted an atomic weapons test, its second.

The North has indicated willingness in principle to return to the six-party forum chaired by its ally China. But it says it wants separate talks with the United States about signing a permanent peace treaty on the peninsula.

South Korea and the United States, which accuse the North of a deadly March attack on a South Korean warship, have responded warily. Japan and Russia are also members of the forum.