iPhone 4 from Europe in South Korea

Hello all,

my friend (she's Korean) is now in Czech Republic for studying. She want to buy new iPhone 4 (it is not locked here) but she's not sure whether she will be able to use it back in Korea.
Does the iPhone 4 from Europe fit Korean mobile network? Also is possible to get there some Korean microSIM card?
When I was in Korea (2007/2008) I remember that they didn't use any SIM cards...