An eagle-eyed neighbour helped catch a man wanted in connection with the murders of three of his family members in South Korea.

The would-be sleuth alerted the Korean Consulate in Auckland after spotting the suspect moving into an Auckland home last week, and recognising him from Korean social media reports about the murders.

He later contacted Korean police who are believed to have alerted their New Zealand counterparts, leading to the suspect's arrest.

The 33-year-old suspect lost name suppression today and can now be named as Kim Sungkwan.

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He is wanted in Korea in relation to the murder of his mother, stepfather and 14-year-old half brother on October 21.

South Korea police said the bodies of the man's mother and son were found with stab wounds in an apartment, and the stepfather's body was found in a boot of a car

Two days after the deaths, Sungkwan reportedly flew to New Zealand with his wife and two young daughters, arriving in Auckland last Tuesday.

Details of the case, the suspect's name and a car he purchased in New Zealand had been discussed widely and circulated on Korean social media.

At 3pm on Friday , an Auckland-based Korean man who thought he recognised Sungkwan approached the consulate to report his whereabouts, Korean media has reported.

The consulate confirmed to the Herald yesterday it had been contacted by the informant, adding that its staff had worked tirelessly with the Korean Embassy and local authorities since the story broke.

According to Korean media reports, the informant had seen Sungkwan with a luxury car that fit the online description.

He thought it was suspicious that the man was moving into a "huge mansion" without any luggage.

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The suspect had also ordered a fridge, washing machine and television to be delivered on the same day.

After approaching the consulate in Auckland, the informant then called Yongin Dongbu Police after searching for their contact details online.

Sungkwan was arrested in Auckland on Sunday evening in a building while his wife was in a car.

He appeared at the North Shore District Court on Monday facing a charge of theft and was granted interim name suppression and remanded in custody.

Name suppression lapsed when Sungkwan reappeared in court today. It was also revealed a warrant has been issued for his arrest in Korea.

Crown Law has now applied for a provisional arrest warrant in New Zealand after receiving a formal request from South Korea in relation to the murder charges.

Sungkwan pleaded guilty to the theft charge today and was further remanded in custody till next month.

When approached by the Herald, police here would not comment on the Korean reports.

"Our only comment is that we are satisfied with the level of cooperation with the Republic of Korean Consulate in Auckland," a spokeswoman said.

"Police [will] continue to liaise with Korean authorities regarding this matter."

A Korean Consulate spokeswoman said: "The Consulate has been working tirelessly with the Korean Embassy in Wellington from the outset of the incident and will continue liaising between the South Korean government and Crown Law in a timely fashion in this matter."