North Korea fires shots at South Korea over government criticism

Kim, the supreme commander of the North Korean military, has ordered front-line units along the heavily fortified frontier to move to a war footing on Friday evening, state media reported.

His nuclear-armed regime, known for being both thin-skinned and fond of saber-rattling, has warned South Korea it faces military action if it doesn't turn off the propaganda loudspeakers by Saturday evening.

The South Korean government, a key U.S. ally, is so far showing no signs of backing down, with its Defense Ministry vowing to retaliate strongly to any additional North Korean provocations.

A senior North Korean official warned that hostilities could be imminent.

"The situation of the country is now inching closer to the brink of war," Ji Jae Ryong, North Korean Ambassador to China told journalists in Beijing on Friday. He blamed South Korea for the situation.

South Korea already responded sharply to the shells that it says North Korea fired Thursday over the demilitarized zone that separates the two countries. The South fired back several dozen shells of its own, according to the Defense Ministry.

No casualties were reported by either side.

It's not the first time that the two sides have briefly traded blows in recent years. They notably exchanged artillery fire over their disputed maritime border in 2010 and machine-gun fire over land in October 2014.

But Thursday's clash was unusual because of the type of weapons used around the demilitarized zone, says Alison Evans, a senior analyst at IHS Country Risk.

"Cross-border attacks have mainly involved small-arms fire or, as in October 2014, anti-aircraft heavy machine guns," she said. "In contrast, there have been frequent exchanges of artillery and rocket fire across the Northern Limit Line (NLL), the de facto maritime border."

Crisis spurred by landmine blasts

South Korean officials said some residents of the area targeted by North Korea on Thursday had to be evacuated, although many of them have since returned home.

The crisis on the Korean Peninsula has been escalating since two South Korean soldiers were seriously wounded on August 4 by landmines in the demilitarized zone.

South Korea has accused North Korea of deliberately planting the mines on a patrol route in the southern part of the zone; an investigation by the U.S.-led United Nations Command in Korea, which monitors the truce at the border, reached the same conclusion.

North Korea has denied it was responsible for laying the mines, snubbing South Korean demands for an apology.

Seoul's response was to resume the cross-border propaganda broadcasts last week for the first time in more than a decade, a move virtually guaranteed to anger the regime in Pyongyang.

Sure enough, North Korea announced over the weekend that the broadcasts were a declaration of war and threatened to blow up the loudspeakers.

A U.S. official told CNN that North Korea was believed to be targeting a loudspeaker position with its artillery on Thursday.

The North Koreans have also been broadcasting propaganda over the border, according to the South.

Is situation likely to escalate?

The question now is whether the situation will escalate further.

North Korea has used similarly alarming language in previous periods of high tensions in the region. In 2013, it announced it had entered "a state of war" with South Korea. That situation didn't result in military hostilities, although North Korea did temporarily shut down the two countries joint industrial zone, which lies on its side of the border.

During that period, North Korea kept up a barrage of bombastic threats against the United States, South Korea and Japan. But at the same time, it was happily accepting tourists and hosting international athletes in Pyongyang for a marathon.

South Korea said Friday that it was limiting the number of its citizens entering the joint industrial zone, but the complex was still operating. There are currently 83 South Koreans in Pyongyang attending a youth soccer event, including players and coaches, according to the South Korean Unification Ministry.

Jamie Metzl, an Asia expert for the Atlantic Council in New York, said he thought it was unlikely that the current crisis would escalate further.

"North Korea has more to gain from conflict theater than from a conflict that would quickly expose its fundamental weakness," he said, suggesting leaders in Pyongyang might be trying to "make trouble because they feel ignored by the international community and feel they have something to gain negotiating their way out of a mini crisis."

But other analysts said the situation could still continue to deteriorate.

The shelling Thursday "raises questions frankly about Kim Jong Un's style of making tension, provocations, escalation -- and whether he knows how to control escalation," said Michael Green, an Asia specialist at the Center for Strategic and International Studies.

U.S. calls on Pyongyang to stop threats

South Korean Defense Minister Han Min-koo warned Friday of the possibility of North Korean provocations after Pyongyang's deadline Saturday for the loudspeakers to be turned off.

The South's President, Park Geun-hye, visited troops at a base south of Seoul, receiving a briefing from military officials on the latest situation, her office said.

The United States, which has roughly 28,000 troops stationed in South Korea, says it is closely monitoring the situation.

"As we've said before, these kinds of provocative actions only heighten tensions," State Department spokesman John Kirby said Thursday, referring to the North Korean shelling. "And we call on Pyongyang to refrain from actions and rhetoric that threaten regional peace and security."

He said that Washington and Seoul are coordinating closely and that the United States "remains steadfast in its commitment to the defense, the security of the peninsula, to our alliance with South Korea."

North Korea has also expressed anger recently over previously planned joint military exercises taking place this week involving tens of thousands of U.S. and South Korean troops.

Pyongyang has said it views such drills as a prelude to an invasion. Seoul and Washington have repeatedly dismissed North Korean requests to call off joint exercises in recent years.