The Dutch senate has given formal approval to a bill legalising euthanasia, making the Netherlands the first country in the world to allow so-called mercy killing.

The vote, the final hurdle for the legislation after it was endorsed by the lower house in November, was passed by 46 votes to 28, with one person absent.

"I hereby declare the proposal adopted," said senate chairman Frits Korthals Altes, after two days of debate.

Health Minister Els Borst had earlier assured senators that the law could not by abused by doctors because of careful supervisory provisions.

The government had urged parliament to back the legislation, arguing that it would hardly change current medical practices in the Netherlands.

'Only God decides'

Demonstrators turned out in force outside the senate buildings, holding prayers and singing hymns.

"We believe in the Lord, and he is the only one who can decide on taking life," said one protester.

Dutch doctors have offered euthanasia to terminally ill patients for at least two decades, and they currently follow guidelines for assisted suicide which were drawn up in 1993.

Government ministers cited public approval ratings of nearly 90% for legalisation of euthanasia and said the law guaranteed the rights of the individual.

"This law will remove the uncertainty for patients and for doctors," said Health Minister Els Borst.

"But [assisted suicide] is and remains a last resort that cannot be seen as an alternative for poor health care."

She added: "Doctors have the right to refuse and patients have the right to choose euthanasia."

Under the new law, euthanasia would be allowed under specific conditions:

• the patient must have an incurable illness
• he or she must be experiencing "unbearable suffering"
• the patient must be of sound mind and have given consent
• the termination of life must then be carried out in a medically appropriate manner.

The legislation goes into force when the Dutch monarch, Queen Beatrix, signs the law and its details are published in the official media, a process expected to take about two weeks.