The man who's wanted in Korea over the deaths of three family members will appear in court on Auckland's North Shore today.

Authorities in Korea say the man fled here soon after the deaths of his mother, stepfather and 14-year-old half-brother.

Police here arrested the 35-year-old yesterday, on a theft charge.

He's a New Zealand resident and returned to the country last week.

Police in South Korea want to speak to him about the murders of his mother, stepfather and 14-year-old half-brother just before he left.

There's been no formal extradition request from Korean authorities yet.