An exchange of artillery fire between North and South Korea on Tuesday provoked angry denunciations from Washington and warnings from Beijing and Moscow that mounting military tensions could provoke a disaster.

Each side blamed the other in the confrontation, which erupted near the Northern Limit Line, the disputed border in the Yellow Sea. Unilaterally declared by the US military at the end of the Korean War in 1953 and never accepted by North Korea, the border has been the scene of repeated clashes.

Scores of North Korean artillery shells struck the island of Yeonpyeong, which lies just two miles from the disputed border and eight miles from the North Korean coast (and 50 miles from the South). The barrage, most of which struck a military base on the island, left two South Korean marines dead and wounded 17 along with three civilians. Hundreds of homes were left in flames, and smoke could be seen billowing over the island.

In the wake of the bombardment, South Korea evacuated some 5,000 civilians from Yeonpyeong and neighboring islands.

Following the barrage, the South fired some 80 shells into North Korea and scrambled fighter planes over the island. There were no immediate reports on casualties from the South Korean attack, but the South Korean military command said that it had inflicted “considerable damage” on coastal bases in the towns of Gaemeori and Mudo in the North.

While the government in Seoul charged that the North Korean military fired first in an unprovoked attack, the government in Pyongyang accused the South of initiating the confrontation by firing into its waters.

“The South Korean enemy, despite our repeated warnings, committed reckless military provocations of firing artillery shells into our maritime territory,” North Korea’s supreme military command said in a statement quoted by the state-run KCNA news agency.

Any conflict on the Korean peninsula directly involves other major powers, above all the United States and China. US president Barack Obama responded Tuesday by committing his government to the defense of South Korea. "South Korea is our ally. It has been since the Korean war," he said. "And we strongly affirm our commitment to defend South Korea as part of that alliance."

The latest confrontation erupted in the midst of the annual “Hoguk” military exercises involving some 70,000 South Korean troops. The nine-day exercises, which are to conclude on November 30, were to include simulated landings by South Korean troops, which Pyongyang charged were a rehearsal for an invasion of the North. The United States usually participates with the South Koreans, though it withdrew from the exercises earlier this month.

North Korea charged that the Southern military had fired shells into its coastal waters in the course of the maneuvers. The South, however, insisted that it had directed its fire to the West, away from the mainland and the disputed border. The South Korean military acknowledged receiving a telephone message from the North on the morning of the artillery duel warning, “The North would not just sit back if the South fired shots into the North Korean territorial waters.”

The Pentagon announced Tuesday that the USS Washington had set sail from its base in Japan for the Yellow Sea in what will be seen as a show of force against North Korea.

The latest exercise is one of a series of joint actions by the US and South Korean military staged in the area in the wake of the sinking last March of the South Korean warship Cheonan, in which 46 sailors lost their lives. The sinking also took place near the Northern Limit Line. While a South Korean investigation concluded that a North Korean torpedo was responsible, Pyongyang has denied any responsibility.

Previous exercises, conducted in July and September, have provoked protests from Beijing, whose territory also borders the Yellow Sea and whose forces fought in the Korean War nearly six decades ago. That war ended in a truce, rather than a peace treaty, meaning that formally a state of war still exists on the Korean peninsula.

South Korea’s President Lee Myung-bak convened an emergency meeting of his cabinet and met with his military commanders following the clash. While warning against any escalation of the tensions, Lee threatened to retaliate with missile strikes against North Korea in the event of any “further provocations.” He said that the North Korean shelling of Yeonpyeong “could be regarded as an invasion of South Korean territory.”

Since taking office in 2008, Lee, a member of the right-wing Grand National Party (GNP), has adopted a hard line against Pyongyang, reversing the so-called Sunshine Policy pursued by his predecessors, which focused on using aid and diplomacy to reduce tensions and open up the North to foreign capitalist investment. Under Lee, new investments have largely ceased and aid has been all but cut off.

There is extensive speculation in the Western media and think tanks as to North Korea’s motives. The clash in the Yellow Sea follows close on the heels of Pyongyang’s revelation to an American scientist that it has developed a 2,000-centrifuge plant for the enrichment of uranium. While it insists that it is for peaceful purposes, the facility opens up a possible new means of producing nuclear weapons.

Many see these actions as an attempt by the North Korean state to pressure both Seoul and the other major powers to resume the so-called six-party talks on nuclear disarmament that began two years ago and to resume aid and lift sanctions that are strangling the impoverished country’s economy.

It is also suggested that the military actions are aimed at solidifying support within the North Korean military for Kim Jong-Eun, who, in his mid-20s, has been tapped to succeed his father, North Korea’s ailing leader Kim Jong-Il. Rumors circulated this week that Kim Jong-Il may have died. “I can neither confirm nor deny his alive status,” Pentagon spokesman Col. David Lapan said Tuesday.

The US think tank Stratfor, which has close ties to American intelligence, suggested another possibility; that the North Korean military is acting on its own. “With the ongoing leadership transition in North Korea, there have been rumors of discontent within the military, and the current actions may reflect miscommunications or worse within the North’s command-and-control structure, or disagreements within the North Korean leadership,” Stratfor said.

Former US Assistant Secretary of State Christopher Hill, who led the US delegation to the six-party talks, sounded a similar warning. “North Korea is going through a very difficult internal transition,” he said. “It’s very clear the North Korean military is unenthused about the proposed succession from Kim Jong-Il to his son. There are a lot of problems there and I think we are seeing that manifest in the way they behave to the outside.”

Washington responded to the clash with a strong condemnation of Pyongyang and unconditional support for South Korea.

President Barack Obama called the North Korean shelling an “outrageous and provocative act.” A statement issued by the White House demanded that Pyongyang “halt its belligerent action” and declared Washington “firmly committed to the defense of our ally, the Republic of Korea, and to the maintenance of regional peace and stability.”

Pentagon officials, however, said that there was no intention to move additional military forces into the region, and the 29,000 US troops deployed in South Korea have not been placed on a heightened state of alert.

Top US military commanders insisted that the US has sufficient forces in the region to attack North Korea. “There is no question that there is a very substantial airpower and joint team capability in the western Pacific, and that has deterrent qualities the North Koreans must respect,” Gen. Norton Schwartz, the Air Force Chief of Staff, told reporters in Washington.

Washington ruled out a resumption of the six-party talks—which included the two Koreas, the US, China, Russia and Japan—in response to the latest confrontation.

Japan also adopted a hard-line response. Japan’s Prime Minister Naoto Kan said he had ordered his ministers “to make preparations so that we can react firmly, should any unexpected event occur. We will make preparations so that whatever happens, we will be able to deal with it.”

China and Russia, however, both insisted that the clash showed the necessity to immediately restart the talks.

“What’s imperative now is to restart six-party talks as soon as possible,” Chinese foreign ministry Hong Lei told reporters in Beijing.

The statement from China did not take sides in the conflict. “We hope the relevant parties do more to contribute to peace and stability on the Korean peninsula,” said the ministry spokesman. He added that China is still seeking to clarify the events leading up to clash. “The situation needs to be verified,” he said.

Russian Foreign Minister Sergei Lavrov, on a visit to the Belarusian capital Minsk, called for both sides “to immediately end all strikes.” He told reporters, “There is a colossal danger which must be avoided. Tensions in the region are growing.”

Washington is utilizing the latest incident to escalate pressure against China. ABC News Tuesday night quoted an unnamed US official as saying that Obama administration was sending “a strong signal to the Chinese that they need to stand up to North Korea.”

China, North Korea’s principal trading partner and political ally, has no interest in facilitating a US military buildup in the region on the pretext of combating North Korean provocations. It is also fearful that turning the screws on Pyongyang will produce a political and economic meltdown that could end in North Korea’s dissolution, sending waves of refugees across its border.

Overshadowing the artillery exchange between North and South Korea is the emerging conflict between the US and China over strategic interests throughout Asia. It is this conflict that lends the clashes across the border drawn at the end of the Korean War nearly six decades ago the potential for escalating into a far larger conflagration.