WASHINGTON (AFP) - An American convicted of killing his five young children was sentenced to death on Thursday (June 13), even after his former wife asked jurors to spare his life because the children loved him.

Lawyers for Timothy Jones, 37, had argued that he is schizophrenic and therefore not competent to stand trial.

Jones was convicted last week of killing his five children - aged one to eight - in 2014.

His former wife stunned the courtroom in South Carolina on Thursday by asking jurors to let Jones live.

"He did not show my children any mercy by any means. But my kids loved him and if I'm speaking on behalf of my kids and not myself, that's what I have to say," Ms Amber Kyzer said, according to press reports.

Ms Kyzer said she had agreed to give Jones sole custody of the children because he made more money as a computer engineer than she did.

Prosecutor Rick Hubbard asked for the death penalty, calling Jones "a monster".

Jurors took less than two hours to announce their verdict.

Jones has said he thought his six-year-old-son was plotting against him with his former wife and allegedly forced him to exercise until he died. He then strangled the other four.

He drove around with his children's bodies for nine days before dumping them in garbage bags on a hillside in Alabama.

Jones was arrested at a traffic checkpoint after an officer caught the smell of decomposing bodies in his car.