Hijjah 19, 1431/November 25, 2010, SPA -- South Korea's president vowed Thursday to boost troops on an island targeted by a North Korean artillery barrage, while the North stridently warned of additional attacks if the South carries out any «reckless military provocations,» according to AP. Seoul and Washington ratcheted up the pressure on China to use its influence on ally North Korea to ease soaring tensions after an exchange of fire Tuesday that left four South Koreans dead _ including two civilians. China urged both sides to show restraint. The North's bombardment of this tiny South Korean island along a disputed maritime frontier _ the first such attack on a civilian area _ alarmed world leaders, including President Barack Obama, who reaffirmed plans for joint maneuvers with Seoul involving a nuclear-powered aircraft carrier in the Yellow Sea starting Sunday. «We should not let our guard down in preparation for another possible North Korean provocation,» South Korean President Lee Myung-bak said during an emergency meeting in Seoul on repercussions of the attack, presidential spokesman Hong Sang-pyo said. «I think a similar North Korean provocation could come at any time.» Yeonpyeong Island, home to military bases as well a fishing community of 1,300 residents, looked like a war zone Thursday, with homes and shops completely flattened and the streets strewn with blackened rubble, mangled window frames and shattered glass. Hundreds of residents have already fled the devastation for the mainland, but a few were still rooting around the rubble looking for personal belonging and spending cold nights in underground shelters. Hong said that South Korea will boost ground troops on Yeonpyeong and four other islands in western waters in response to this week's attack, reversing a 2006 decision calling for an eventual decrease. He declined to discuss specifics for the increase, but said troops there currently amount to about 4,000. His comments came as South Korea's defense chief visited the island, located about 50 miles (80 kilometers) from the port of Incheon west of Seoul but just 7 miles (11 kilometers) from North Korean shores. The military was analyzing debris from North Korea's artillery and has not ruled out North Korea's use of thermobaric bombs, which burn more violently and increase casualties and property destruction, a Joint Chiefs of Staff official said. He asked not to be identified, saying he was not authorized to speak to reporters. The two Koreas are required to abide by an armistice signed at the close of the three-year war, but the North does not recognize the maritime line drawn by U.N. forces in 1953 and considers South Korean maneuvers near Yeonpyeong island a violation of its territory. The attack added to animosity from the March sinking of a South Korean warship in nearby waters that killed 46 sailors in the worst military attack on the nation since the Korean War. Skirmishes occur from time to time around the sea border, but Tuesday's attack was the first to target civilians and raised concerns about escalating hostilities leading to another war. The shelling also comes as North Korea is undergoing a delicate transition of power from leader Kim Jong Il to his young son Kim Jong Un. The son, who is in late 20s, was made a four-star general and nominated to high-ranking Workers' Party posts in the first steps toward eventually succeeding his father. The previously scheduled U.S.-South Korean drills set to begin Sunday and involving the carrier USS George Washington are sure to infuriate North Korea. The North made no specific mention of those exercises in its statement but warned that its military would «launch second and third strong physical retaliations without hesitation if South Korean warmongers carry out reckless military provocations.» The North also said Washington was to blame for the South Korean artillery drills on Yeonpyeong that prompted the North to respond with its artillery barrage Tuesday. Washington «should thoroughly control South Korea,» it said. The warning was issued by North Korea's military mission at the truce village of Panmunjom and was carried by the official Korean Central News Agency. South Korea says its artillery exercises Tuesday were aimed away from North Korea, and a top military official on the island Thursday showed reporters a trajectory heading to the southwest. «North Korea argues that we fired at them first, but this is the direction that we fired,» Lt. Gen. Joo Jong-hwa said. Meanwhile, the Obama administration urged China to rein in ally North Korea, with the chairman of the Joint Chiefs of Staff, Adm. Mike Mullen, saying: «We really think it's important for the international community to lead, but in particular China.» Chinese Premier Wen Jiabao called on all sides to show «maximum restraint.» He repeated calls for renewed six-nation talks aimed at persuading North Korea to dismantle its nuclear programs. Wen said those talks, involving the two Koreas, China, Russia, Japan and the United States, are the best way to ensure stability on the peninsula and its denuclearization. Wen's remarks were made in Russia on Wednesday on a state visit and posted on the Chinese Foreign Ministry's website. South Korea said it will increase diplomatic efforts to get China, which supplied North Korea with troops during the Korean War and remains its main ally and biggest benefactor, to put pressure on Pyongyang. On Thursday, the coast guard transported two white coffins carrying the bodies of civilians pulled from the rubble Wednesday. In Seongnam, just outside Seoul, military officers and family members mourned the two marines killed in the attack, laying flowers and burning incense at an altar. Funerals are to take place Saturday. Yeonpyeong residents arrived in Incheon with harrowing tales of fiery destruction and narrow escapes. Survivor Ahn Ae-ja said the artillery barrage caught her by surprise. «Over my head, a pine tree was broken and burning,» Ahn told AP Television News on Wednesday. «So I thought 'Oh, this is not another exercise. It is a war.' I decided to run. And I did.» About 10 homes suffered direct hits and 30 were destroyed in the barrage, according to a local official who spoke by telephone. She asked that her name not be used. «I heard the sound of artillery, and I felt that something was flying over my head,» said Lim Jung-eun, 36, who fled the island with three children, including a 9-month-old strapped to her back. «Then the mountain caught on fire.» The shower of artillery from North Korea was the first to strike a civilian population. In addition to the two marines and two civilians killed in the exchange, at least 18 people _ most of them troops _ were wounded. Officials in Seoul said there could be considerable North Korean casualties but there was no mention in North Korean state media of casualties.