A MENTALLY ill man, jailed three years for stabbing his wife and their unborn child with a sword, will now have to serve two more years in prison.

The Court of Appeal on Thursday increased Han John Han's jail term from three to five years after the prosecution appealed, arguing that he had got away too lightly.

In delivering the stiffer sentence, Justice Andrew Phang said the court could not ignore the fact that two lives had been lost.

While the Appeal judges acknowledged that Han, 51, a project manager, had suffered from a delusional disorder, they said the stiffer sentence addressed the public interests and took into account Han's need for rehabilitation.

Han was jailed three years on Jan 15 after he admitted plunging a 50cm-long sword into his wife's chest, killing her and their unborn child

He believed that his wife, Madam Fu Xiaopei, 39, was using black magic to put a hex on him and that someone was trying to harm him.

In jailing Han three years for manslaughter, the trial judge, Justice Choo Han Teck, considered his unblemished record and accepted that he was no longer a danger to himself or to others.

The prosecution appealed against the jail sentence, charging that Han's homicidal act was deliberate, unprovoked, clearly intended to be fatal - and pressed for an eight-year prison term.

Han's family members, who were in court on Thursday, declined to speak reporters.