AP

In a historic ruling, an international court has convicted former Liberian President Charles Taylor of aiding and abetting war crimes and crimes against humanity for supporting notoriously brutal rebels in neighbouring Sierra Leone in return for "blood diamonds".

Taylor is the first head of state convicted by an international court since the post-World War II Nuremberg military tribunal.

"Today is for the people of Sierra Leone who suffered horribly at the hands of Charles Taylor and his proxy forces," prosecutor Brenda Hollis said on Thursday.

"This judgment brings some measure of justice to the many thousands of victims who paid a terrible price for Mr Taylor's crimes."

Prosecutors and defence lawyers both said they would study the lengthy judgment to see if there were grounds for appeal.

Taylor's lawyer, Courtenay Griffiths, slammed the conviction as based on "tainted and corrupt evidence". He claimed prosecutors paid for some of the evidence.

Griffiths said Taylor took the verdicts in his stride. "Mr Taylor has always been a stoic individual and he continued to display that stoicism," Griffiths told reporters.

Presiding Judge Richard Lussick said the 64-year-old warlord-turned-president provided arms, ammunition, communications equipment and planning to rebels responsible for countless atrocities in the 1991-2002 Sierra Leone civil war and was repaid by the guerrillas in so-called "blood diamonds" mined by slave labourers. Lussick called the support "sustained and significant".

"Mr Taylor, the trial chamber unanimously finds you guilty" of 11 charges, including terror, murder, rape and conscripting child soldiers, Lussick told Taylor.

Taylor stood and showed no emotion as Lussick delivered the guilty verdicts at the Special Court for Sierra Leone. Lussick scheduled a sentencing hearing for May 16, and said sentence would be announced two weeks later. Taylor will serve his sentence in Britain.

The court does not have maximum sentences or the death penalty. In the past, convicted Sierra Leone rebel leaders have received sentences of up to 52 years.

Human rights activists hailed the convictions as a watershed moment in the fight against impunity for national leaders responsible for atrocities.

"Taylor's conviction sends a powerful message that even those in the highest-level positions can be held to account for grave crimes," said Elise Keppler of Human Rights Watch.

"Not since Nuremberg has an international or hybrid war crimes court issued a judgment against a current or former head of state. This is a victory for Sierra Leonean victims, and all those seeking justice when the worst abuses are committed."

Thousands of survivors of Sierra Leone's brutal civil war celebrated after learning of the conviction.

Jusu Jarka, who lost both of his arms during the fighting in 1999, was among those closely watching the verdict.

"I am happy that the truth has come out ... that Charles Taylor is fully and solely responsible for the crimes committed against the people of Sierra Leone," he said.

Crowds who had gathered in Freetown, Sierra Leone's capital, sighed with relief when the conviction was announced. While the reaction was subdued, anger was on display on a series of posters. One read: "Shame on you Charles Taylor. Give us your diamonds before going to prison."

Taylor had pleaded not guilty to all counts, claiming in seven months of testimony in his own defence that he was a statesman and peacemaker in West Africa.

While judges convicted him of aiding and abetting atrocities by rebels, they cleared him of direct command responsibility, saying he had no direct control over the rebels he supported.

The only other head of state convicted by an international court was a Nazi naval commander, Karl Doenitz, who briefly led Germany after Adolf Hitler's suicide and was convicted by a military tribunal at Nuremberg after World War II.

Others have been indicted but not convicted - yet.