Disgraced South Africa's Paralympic track star Oscar Pistorius has filed an appeal against his conviction for murdering his girlfriend, Reeva Steenkamp.

Pistorius killed Steenkamp in February 2013 after firing four times through a locked toilet door.

A manslaughter verdict was overturned last month and a murder verdict introduced in its place.

The athlete's defence has lodged papers at the Constitutional Court today, urging a review of his murder conviction.