SEOUL (REUTERS) - The two Koreas traded heavy machine-gun fire across their border Friday, as "missing" North Korean leader Kim Jong Un's failed to attend a key political event, fuelling further speculation about his physical health and political future.
No casualties were reported in the exchange of fire which South Korea said was triggered by the North Korean military trying to shoot down balloons carrying anti-Pyongyang leaflets that were launched by activists in the South around 2:00pm (0500 GMT).
Some rounds fell on the South side which then responded with high-calibre machine gun fire "towards the North's guard posts," a defence ministry spokesman said.
There was a further exchange of fire 10 minutes later, he added.
Local residents of Hwangsan-ri township in the border area of Yeoncheon were evacuated to shelters as a precaution.
While naval confrontations along the Koreas' disputed maritime border occur from time to time, any military engagement across the heavily-militarised land frontier is extremely rare.
In 2010, the North shelled the South Korean border island of Yeonpyeong, killing four people and briefly sparking fears of a full scale conflict.
The balloon launch from Hapsuri was one of several planned to coincide with North Korea's celebration of the 69th anniversary of its ruling Workers' Party.
Seoul allowed the exercises to go ahead, despite prior warnings from Pyongyang of "catastrophic" consequences.
Some of the balloons carried messages denouncing North Korean leader Kim Jong-Un, who has not been seen in public for more than a month.
Competing theories for his disappearance range widely from an extended rest period to a leadership coup, via a long list of possible illnesses and ailments including broken ankles, gout and diabetes.
On Friday, Kim was not listed by the state KCNA news agency among the officials who visited the mausoleum housing the remains of his father and grandfather - an annual show of respect to mark the party anniversary.
Kim was last seen on September 3 and his absence Friday was considered significant as he had attended the ceremony each year since coming to power following the death of his father in 2011.
A heavy smoker, Kim has shown striking weight gain over the past year and recent TV footage had shown him walking with a pronounced limp.
Cheong Seong-Chang, an analyst at the Sejong Institute think-tank in Seoul, said his disappearance was almost certainly down to a health problem that would have little impact on his leadership - at least in the short term.
"But if he's forced to stay away for an extended period, it could cause murmurings within the political elite and weaken Kim's control," Cheong said.
South Korea, which has largely distanced itself from the disappearance rumours, said it saw no indication that Kim was no longer in charge.
Unification Ministry spokesman Lim Byeong-Chul noted numerous reports in the North Korean state media of Kim exercising his authority.
"Judging from these, it seems that Kim Jong-Un is ruling normally," Lim said, adding that the government had no specific intelligence on Kim's health.
In a front-page editorial on Friday, the Rodong Sinmun described Kim as the symbol of the ruling party's "dignity and invincibility", and said his authority should be protected by all means necessary.
What little light North Korea has deemed necessary to shed on the rumours surrounding Kim's absence has only added to the confusion.
State media alluded at one point to his "discomfort", but one member of a top-level North delegation that visited South Korea last week insisted Kim had no health problem at all.
It is by no means unprecedented for a North Korean leader to drop out of the public eye for a while.
But it is more noticeable with Kim, who has maintained a particularly pervasive media presence since coming to power after the death of his father Kim Jong-Il in 2011.
Bruce Bennett, a senior defence analyst with the RAND corporation, said Kim would not want to appear in public if he was physically incapacitated.
"He certainly doesn't want to be seen while he is sick and looking weak," Bennet said.
"Looking weak is not good for a North Korean leader who is trying to maintain control."