"North Korea wants to get the U.S. to direct bilateral negotiations by using the missile card, " said Paik Hak-soon, a North Korea expert at the Seoul-based Sejong Institute.

NPR: Bush Calls for Unity, Condemns North Korean Tests

Ms Park's main opponent looks likely to be Sohn Hak-kyu.

ECONOMIST: The race to succeed the president gets under way

He is a maverick in a country whose financial institutions have long operated around hak-yeon, ji-yeon and hyul-yun (school, hometown and kinship ties) and government diktat on who to lend to and how much.

CNN: HERE COME THE MAVERICKS