A mother who murdered her two children and stuffed them into suitcases stashed inside a storage locker was on Wednesday sentenced to life imprisonment in New Zealand.

Hakyung Lee, a New Zealand citizen originally from South Korea, was earlier this year found guilty of killing her children in a grisly crime dubbed the country's "suitcase murders".

High Court judge Geoffrey Venning sentenced Lee to life imprisonment with a minimum non-parole period of 17 years, saying she had killed children who were "particularly vulnerable".

Flanked by security guards and a translator, 45-year-old Lee showed little reaction as the sentence was handed down.

Lee killed her son Minu Jo and daughter Yuna Jo, aged six and eight, with an overdose of prescription medication in 2018.

The bodies were not found until 2022, when an unsuspecting family pried open the contents of an abandoned storage locker they bought in an auction.

Lee, who had long since changed her name and fled the country for South Korea, was extradited to face trial in New Zealand.

The sentencing hearing on Wednesday heard how the murders had left deep emotional scars on Lee's family.

"If she wanted to die why didn't she die alone?" Lee's mother Choon Ja Lee said in a statement read to the court.

"Why did she take the innocent children with her?"

Lee's brother-in-law said the children's other grandmother was sick with cancer and still did not know about the murders.

Sei Wook Cho said his "daily existence is a time bomb of fear" that the grandmother would find out, according to a statement also read to the court.

"It was my late brother's will that I protect them," read the statement.

"This is an ongoing sentence from which I can never be paroled."

The trial hinged not on whether Lee had murdered her children – which she had confessed to – but whether she knew her actions were morally wrong.

Her lawyers had argued she was not guilty by reason of insanity and that the death of her husband in 2017 sent her into a depressive spiral.

A forensic psychiatrist testified for the defence about Lee's mental state – describing depression, suicidal thoughts, guilt, and a belief that killing her children was the right thing to do.

But the prosecution had argued she knew what she was doing, pointing to her efforts to hide the bodies before fleeing the country. (AFP)