UPDATE: North Korea warns of retaliation; Seoul orders security beefed up
South Korea's president vowed Thursday to boost security around islands near the site of this week's artillery attack by North Korea.
His order to beef up security came as North Korea warned of more "retaliation" if Seoul carries out "reckless military provocations."
"We should not let our guard down in preparation for another possible North Korean provocation," South Korean President Lee Myung-bak said at an emergency government meeting Thursday.