SEOUL — North Korea Friday fired artillery into the sea near its disputed border with South Korea for a third successive day, Seoul's military said.

The communist state fired 20 shells between 7.50 am and 11.50 am, a spokesman for the Joint Chiefs of Staff (JCS) told AFP.

He said shells landed in North Korean waters off South Korea's Yeonpyeong island. They dropped further away from the borderline than on Wednesday and Thursday.

Seoul's defence ministry said it is considering shipping more artillery and advanced radar to two border islands in response to the shelling, which began Wednesday near the tense frontier in the Yellow Sea.

The North says it is conducting a routine artillery drill but Seoul and Washington criticise the gunfire as provocative.

The ministry said the North Wednesday fired 300 shells -- far more than earlier reported -- and 50 on Thursday. The JCS has said it has information the artillery drills will end later Friday.

Analysts say the display of firepower is partly an attempt by the North to raise tensions, to press its case that a formal peace pact on the heavily armed peninsula is essential.

South and North Korea have remained technically at war since their 1950-53 conflict ended only in an armistice.

The North refuses to return to six-nation nuclear disarmament talks until the United States agrees to discuss a formal peace treaty.

Seoul has reacted calmly to the barrage and has said it will go ahead with talks scheduled for Monday in North Korea about a joint business project.

South Korean Marines fired 100 warning shots when the barrage began Wednesday but did not respond after that.

Officials say the North's shells have all landed on its side of the borderline, apparently indicating it does not want to go too far.

Seoul will "seriously consider" reinforcing Baengnyeong and Yeonpyeong islands, Defence Minister Kim Tae-Young was quoted as telling parliament.

The head of parliament's defence committee, Kim Hak-Song, quoted the minister's remarks to a closed session of his committee. The defence ministry confirmed the substance of the minister's comments.

The ministry will consider deploying more K-9 self-propelled guns on the islands plus Firefinder radars which can track the source of incoming fire.

"Such radars are crucial for our side to launch quick and precise counter-attacks," a JCS spokesman said.

Despite this week's rise in tensions, President Lee Myung-Bak said he is willing to meet North Korean leader Kim Jong-Il this year if it would help nuclear disarmament efforts.

"I'm always ready to meet with Chairman Kim Jong-Il," Lee said in an interview with the BBC Thursday in Davos, where he attended an economic forum.

His office released a transcript Friday.

"However, if we meet, we have to engage in fruitful dialogue and hold enough discussions on the North Korean nuclear issue," Lee said.

"When we get into a situation where (such a summit) may be helpful for peace on the Korean peninsula and the settlement of the nuclear issue, there is no reason why I can't meet him, even within this year."

Lee said the North's actions could be aimed at delaying its return to the six-party talks, or pressing demands for a peace treaty and for inter-Korean dialogue.

"However, this is not a good method," he said.

South Korean media have reported that the two Koreas held talks last year about a possible summit following months of hostility, but that the talks broke down due to differences over conditions.

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