SEOUL—Talks between North and South Korea to end a military standoff ran through the night and into Monday, with Seoul accusing Pyongyang of trying to increase its leverage by deploying large numbers of submarines and artillery.

South Korean President Park Geun-hye indicated that negotiators had made little progress in defusing tensions, issuing a fresh call on North Korea to apologize for attacks earlier this month that sparked this latest crisis between the Cold-War rivals.

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