Former Liberian president Charles Taylor has appealed his war crimes and crimes against humanity convictions and his 50-year sentence, calling them a miscarriage of justice.

Prosecutors on Thursday also appealed the Special Court for Sierra Leone's decision to acquit Taylor on more serious charges and urged judges to increase his sentence to 80 years.

Taylor, 64, became the first former head of state since the Second World War to be convicted by an international war crimes court when he was found guilty in April of aiding and abetting murderous rebels during Sierra Leone's bloody civil war.

He was cleared of directly ordering atrocities such as massacres and mutilations carried out by the rebels.