Three doctors in Belgium have been cleared of wrongdoing in a landmark euthanasia case for the country.

The two doctors and psychiatrist had been accused of the unlawful killing of Tine Nys, after she was administered with a lethal injection in 2010.

She had spoken of her desire to end her life and, two months prior to her death, had been diagnosed with Asperger's Syndrome.

The three doctors on trial had signed off on her euthanasia but were prosecuted after Nys' family challenged their decision.

Belgian law permits euthanasia in cases of "constant and unbearable physical or mental suffering that cannot be alleviated".

Nys' family argued that her case did not meet this requirement and that she suffered from depression triggered by a relationship breakdown that they believed was still treatable.

The doctors, who denied any wrongdoing, were acquitted at a court in Ghent on Friday after a two-week trial.

Defence lawyer Walter Van Steenbrugge said the verdict was "a relief for all doctors who have to carry out such tough tasks".

"If this would have gone the other way, so many doctors would have been in real deep trouble," he said.

Right To Life UK spokesperson Catherine Robinson said the case "highlights the lack of compassion in countries with assisted suicide and euthanasia laws but also draws attention to the risks and dangers of legalising assisted suicide and euthanasia".

"Tine Nys was a physically healthy woman with her future ahead of her. She should have been offered care and support to alleviate her short-term suffering," she said.

"Assisted suicide clears the way for despair and hopelessness. Where hardship and suffering is, assisted suicide is allowed to take the place of care and compassion as a response."