Belgian lawmakers have voted overwhelmingly in favour of extending the country's euthanasia law to children under 18.

The 86-44 vote on Thursday in the House of Representatives, with 12 abstentions, followed approval by the Senate last December.

The law empowers children with terminal ailments who are in great pain to request to be put to death if their parents agree and a psychiatrist or psychologist find they are conscious of what their choice signifies.

Legislators have clashed sharply over the bill. Proponents view it as a question of mercy, while critics say the bill has been rushed and lacks a medical rationale.

"Our responsibility is to allow everybody to live, but also to die, in dignity," said Karine Lalieux, a Socialist member of the House of Representatives.

Sonja Becq, a Christian Democrat, denounced the bill, saying modern-day science is capable of relieving pain in very sick children until their illness runs its natural course.

"We cannot accept that euthanasia be presented as a 'happy ending'," she said.

Church protesting

Protests over the child-euthanasia legislation have gripped Belgium for days.

The Catholic church staged "a day of fasting and prayer" in protest earlier this month, and about 160 pediatricians on Wednesday petitioned lawmakers to postpone the vote on the grounds that it was ill-prepared and unnecessary.

"Pain can be eased nowadays; there's been huge progress in palliative care," Nadine Francotte, a cancer specialist in the city of Liege, told the AFP news agency.

But Dominique Lossignol, a palliative specialist at the Bordet cancer clinic in Brussels, said that doctors "do not have control over all types of pain, either physical or moral".

"Children are capable of taking such a decision," he said.

A public survey found 75 percent of Belgians supported extending the euthanasia law to children.

The law will go into effect when signed by Belgium's monarch, King Philippe. The king was not expected to oppose the measure.