Seoul , South Korea ( CNN ) -- North Korea will launch additional attacks on South Korea if it continues `` reckless military provocation , '' North Korean state media said Thursday . Meanwhile , South Korea said Thursday that it will strengthen and supplement its rules of engagement in the Yellow Sea , following Tuesday 's shelling by North Korea . Marine forces based in five islands near North Korea and the disputed Northern Limit Line also will be reinforced , a government spokesman said . The tense maritime border between the two Koreas has become the major military flash point on the peninsula in recent years . The announcement followed a meeting between President Lee Myung-bak and his economic and security ministers Thursday morning in Seoul . The meeting began with a moment of silence for the two South Korean marines and two civilians who died in Tuesday 's attack on Yeonpyeong Island in the Yellow Sea . The shelling also injured 15 South Korean soldiers and three civilians . The attack will lead to a plan being drafted to deal with civilian safety on the five islands in the Yellow Sea , the spokesman said . No details were immediately offered about the plan , but Lee on Wednesday ordered the strengthening of civilian shelters on the islands . The islands include Yeonpyeong and Baengnyeong , off which the South Korean warship Cheonan was sunk in March , killing 46 sailors . Seoul blamed Pyongyang for the torpedo attack , which the North has denied . The Lee administration also will continue to closely monitor capital markets and foreign exchange rates , prepared to take preventative measures as needed , the spokesman said . The shelling sent ripples through South Korea 's stock market , which has rebounded . South Korea 's economic and security ministries will cooperate closely , and the administration will publicize developments in real time to address major concerns and squelch rumors , the administration said . The attack on Yeonpyeong Island was the first direct artillery attack on South Korea since the Korean War ended in 1953 . The United States quickly offered support following Tuesday 's shelling , affirming that it would hold joint military drills with South Korea starting Sunday . The USS George Washington sailed toward volatile waters off the Korean peninsula Wednesday for the exercises in a show of force designed to deter a further escalation of hostilities with North Korea . The exercises were billed as defensive in nature and were a more measured response than the retaliation initially urged by South Korea after North Korea 's shelling of Yeonpyeong . `` It is a long-planned exercise , '' said Adm. Mike Mullen , chairman of the U.S. Joint Chiefs of Staff . `` That said , it is meant to send a very strong signal of deterrence and also work with our very close allies in South Korea , '' Mullen said on CNN 's `` Fareed Zakaria GPS . '' `` We 're very focused on restraint -- - not letting this thing get out of control . The South Koreans so far have responded that way . Nobody wants this thing to turn into a conflict . '' CNN 's Stan Grant contributed to this report .
N. Korea says `` reckless military provocation '' will bring new attacks . S. Korea says marine forces based in five islands will be reinforced . The islands are near the North Korea maritime border .