A high proportion of deaths classed as euthanasia in Belgium have involved patients who have not requested that a doctor ends their lives, a new study has found.

Researchers have discovered that seriously ill or elderly patients taken to hospitals are often given lethal doses of drugs to end their lives even though they have not asked to be killed.

The practice, known as "involuntary euthanasia", is against the law in Belgium. Critics say it is barely distinguishable from murder.

But "voluntary euthanasia", where patients request that a doctor ends their lives, has been permitted in the country for the last eight years.