Two children with cancer aged nine and 11 became the youngest in the world to be euthanised, it has been revealed.

They were given lethal injections in Belgium under the world's only law that allows children of any age to choose to end their lives.

The Belgian laws say children must have a terminal disease and be suffering unbearably.

They must also be judged to have the mental capacity to make the decision and have parental consent.

Two children aged nine and 11 became the youngest in the world to be euthanised, it has been revealed

Supporters of the law say it is cruel to force a child to suffer against their will while opponents say children are too young to make the decision to die.

A report on 17 July revealed three children were among thousands of people to have died under Belgium's radical euthanasia regime between January 1, 2016 and December 31, 2017.

The report did not reveal the children's ages but a Belgian official has now disclosed those details to the Washington Post. The third child was 17.

The annual number of euthanasia cases across all age groups has multiplied almost fivefold in ten years in Belgium.

The practice was legalised in the country in 2003 – a year after the Netherlands, where the minimum age is 12. In 2007, 495 Belgians chose to die this way.

Latest figures reveal there were 2,028 such deaths in the country in 2016 and 2,309 in 2017 – a 14 per cent year-on-year rise.

Two of the children died in 2016 and one in 2017. Their names were not given but all were understood to have had cancer.

Three children were euthanised under the world's only law that allows children of any age to choose to be put to death

While the Netherlands does not allow children under 12 to choose death, Belgium's decision in 2014 to extend its euthanasia laws to all minors provoked outrage in the country and internationally.

Many religious groups argued the country's laws 'trivalise' death and went a 'step too far'.

Of the 4,337 to opt for assisted dying in Belgium in 2016/17, most were cancer patients.

However 710 were largely elderly people who suffered from a series of comparatively minor conditions such as blindness and incontinence.

A further 77 chose to die because of unbearable psychiatric suffering. A further 19 young people between 18 and 29 decided to end their lives.

Crossbench peer Lord Carlile, co-chairman of Living and Dying Well, a parliamentary group opposed to euthanasia, said he was 'profoundly shocked' both by the deaths of the children and by the soaring number of euthanasia cases.

He added: 'No parent or public authority has the power to take away the life of anyone who is a child, whoever they are.'

Professor Wim Distelmans, head of Belgium's Federal Commission for Euthanasia Control and Evaluation, said 'more and more' elderly people 'no longer accept' polypathology – non-terminal conditions such as sight and hearing loss and incontinence – and opt to die instead.

In February, neurologist Dr Ludo Vanopdenbosch resigned from the commission, which is controversially made up of many pro-euthanasia doctors, in protest at the unchecked killings of dementia patients.