LEIDSCHENDAM, Netherlands -- Prosecutors urged judges Tuesday to reject former Liberian President Charles Taylor's appeal against his war crimes conviction and 50-year prison sentence, saying the court should hold "lords of war" as responsible for atrocities as the machine-gun-wielding killers they support.

Taylor was found guilty in April 2012 of aiding and abetting Sierra Leone rebels, becoming the first former head of state since World War II to be convicted by an international war crimes court. He was convicted of 11 counts of war crimes and crimes against humanity, including murder, rape, torture and the use of child soldiers.

But as Taylor watched silently from his seat in the courtroom Tuesday, one of his lawyers, Christopher Gosnell, said judges at his trial had a "deep and fundamental" misunderstanding of the legal notion of "aiding and abetting."

He compared Taylor's actions with those of other governments that provide support to rebel groups, saying Taylor "had no criminal intent" in aiding armed groups in Sierra Leone. Another of his lawyers, Eugene O'Sullivan, called Taylor's sentence "manifestly excessive."

Taylor's defence lawyers have put forward 45 grounds to appeal his conviction and sentence, alleging that trial judges made dozens of factual and legal errors. Prosecutors in turn argued he should have been convicted not just of aiding and abetting rebels, but of ordering or instigating their crimes -- considered more serious.

From his presidential palace in Liberia, Taylor provided arms, ammunition and other support to rebels responsible for murdering and mutilating their enemies in Sierra Leone's decade-long civil war that ended in 2002 with some 50,000 dead. In return, the rebels paid him in so-called "blood diamonds" mined by slave labour in Sierra Leone and Taylor gained influence in the volatile west African region.

Taylor claimed he was only trying to help stabilize the war-torn country, but trial judges rejected that argument.

"The lives of many more innocent civilians in Sierra Leone were lost or destroyed as a direct result of his actions," Presiding Judge Richard Lussick said when he sentenced Taylor last year.

Rebel fighters in Sierra Leone gained international notoriety for hacking off the limbs of their victims and carving their groups' initials into opponents. The rebels developed gruesome terms for the mutilations that became their chilling trademark: They would offer their victims the choice of "long sleeves" or "short sleeves" -- having their hands hacked off or their arms sliced off above the elbow.

Taylor ran Liberia from 1997 to 2003. As his government fought a two-front rebellion in 2003, he stepped down and fled to Nigeria under international pressure. Three years later, Taylor was finally arrested and sent to the Netherlands.

Prosecutors want Taylor's 50-year sentence -- already effectively a life sentence for the 64-year-old former president -- raised to 80 years to send a message to leaders who facilitate atrocities.

"Those are the promoters of war, the lords of war that sell arms to groups engaged in these conflicts," prosecution lawyer Nicholas Koumjian said.

He likened Taylor's aid to rebels to the case of a Dutch businessman, Frans van Anraat, who was convicted by a Dutch court for selling chemicals to Saddam Hussein knowing the Iraqi dictator would use them to make poison gas.

Koumjian's comments aimed to counter Taylor's arguments that he should not have been convicted because his support for rebels was not deliberately designed to help them kill and maim.

Gosnell said that for judges to convict Taylor of aiding and abetting crimes, his help must be "connected to a specific crime and there must be a substantial contribution to that crime."

Instead, he said trial judges applied a standard "so broad that it would in fact encompass actions that are today carried out by a great many states in relation to their assistance to rebel groups or to governments that are well-known to be engaging in crimes."

In their written appeal, Taylor's lawyers said "the Trial Chamber's approach extends criminal liability far beyond its proper bounds as recognized in international law."

Taylor's lawyers also argued that his conviction was based in part on uncorroborated hearsay evidence that should not have been admitted. They have asked judges to overturn all of Taylor's convictions.

The appeals chamber is expected to take months to reach its judgment.