SEOUL — Call them the shots heard round the world.

South Korea fired live artillery into the Yellow Sea on Monday afternoon from Yeonpyeong Island as officials scrambled at the United Nations and behind the scenes to try to keep the 90-minute exercise from escalating already white-hot tensions on the Korean peninsula.

The exercise was designed to increase military readiness, South Korean officials said, in the wake of a Nov. 23 North Korean attack on the island that left four people dead. North Korea threatened to retaliate if the drill was held in the area of the disputed maritime border between the two Koreas.

U.S. Forces Korea spokesman David Oten said Monday afternoon the exercise “went according to plan and there has been no response.”

He stressed the live-fire drill was a routine training event about which North Korea officials had been notified.

“They knew it was coming,” he said.

A group of about 20 U.S. soldiers and Marines participated in the drill, and U.N. Command observers representing seven countries also were on hand, Oten said.

Monday’s exercise came just hours after the U.N. Security Council met in New York, and New Mexico Gov. Bill Richardson – a former U.S. ambassador to the U.N. – met with officials in North Korea in hopes of defusing the hostilities on the peninsula, which appear to have the two Koreas as close as they have come in decades to a resumption of the Korean War.

On March 26, 46 South Korean sailors were killed when warship Cheonan sank near the disputed maritime border in the Yellow Sea. A South Korean-led international team of investigators determined the ship was taken down by a North Korean torpedo. North Korea has maintained it had nothing to do with the Cheonan incident.

On Nov. 23, Two South Korean marines and two civilians were killed during a shelling of Yeonpyeong, an act for which North Korea did take responsibility, saying it was a response to a South Korean “provocation” of firing toward the North. South Korea has disputed that claim.

The Associated Press reported that the U.S. and other members demanded Sunday that the U.N. Security Council condemn North Korea for the two deadly attacks, but China’s representatives strongly objected.

Russia’s U.N. Ambassador Vitaly Churkin, who called the emergency council meeting, said that after eight hours behind closed doors, “We were not successful in bridging all the bridges.”

U.S. Ambassador Susan Rice added, “The gaps that remain are unlikely to be bridged.”

Meanwhile, Richardson was urging North Korean officials to exercise restraint in response to the live-fire drill. CNN reported that during Richardson’s unofficial visit and his meeting with high-level officials, North Korea agreed to a series of actions, including allowing the return of U.N. inspectors to nuclear facilities and to consider a proposal that a military commission be formed with representatives of the U.S. and the two Koreas.

CNN also reported that a top North Korean general offered Sunday to help return the remains of several hundred U.S. troops killed during the Korean War. Maj. Gen. Pak Rim Su told Richardson that the bodies were discovered recently in North Korea.

Korean media outlets reported that both Koreas appeared to take steps Monday for a possible escalation of hostilities.

South Korea scrambled F-15K fighter jets and deployed close to a dozen naval ships to the waters off the west coast of the peninsula. The South also ordered hundreds of residents of islands near the disputed maritime border into underground bunkers.

North Korea reportedly removed covers from coastal artillery guns and deployed some artillery batteries.

Prior to the drill, AP reported that South Korean President Lee Myung-bak urged his countrymen to be more united and vigilant about North Korea.

“The highest level of national security comes from unity among the people,” he said, adding that North Korea provokes South Korea when “our public opinion is divided.”

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