South Korea's president has urged North Korea to embrace a "new era" by using its recent leadership handover as an opportunity to transform Korean ties, but warned that Seoul would respond sternly to any provocations.
Lee Myung-bak's comments in a nationally televised speech come as the young son of Kim Jong Il takes power in North Korea as supreme commander of the military and ruling party leader after Kim's death last month.
The North said on Sunday that its citizens should turn themselves into "human shields" to defend the son, Kim Jong Un, "unto death".
Mr Lee said Kim Jong Il's death is "portending a sea change" for the Korean peninsula.
"If North Korea comes forward with a sincere attitude, it will be possible for us to work together to open a new era," he added.
North Korea said last week that it would never deal with Mr Lee, but Kim Jong Un's rise could offer a chance to improve ties that have suffered since Mr Lee took office in 2008 and ended a no-strings-attached aid policy toward the North.
The young Kim had a brief meeting in Pyongyang late last month with a former South Korean first lady and a business leader who were leading private mourning delegations to pay respects to Kim Jong Il.
Mr Lee said the Korean peninsula is at a turning point and "new opportunities always emerge amid such changes". However, he also warned that South Korea would sternly respond to any North Korean provocation. In 2010, 50 South Koreans died in attacks blamed on the North, though the Koreas have met in recent months for preliminary nuclear discussions.
North Korea, which has tested two atomic devices since 2006, has said it wants to return to long-stalled six-nation talks on halting its nuclear weapons programme in return for aid. Washington and Seoul, however, have insisted that the North first shows progress on past disarmament commitments.
If North Korea halts its nuclear activities, Mr Lee said in his speech, negotiations could resume.