New Zealanders have voted to legalise euthanasia in the preliminary results of a referendum held in mid-October after years of emotional debate.

Friday's results showed 65.2% of voters supported the End of Life Choice Act 2019 coming into force as a new law.

It will allow terminally ill people with less than six months to live the opportunity to choose assisted dying if approved by two doctors.

The referendum is binding and the law will come into effect in November 2021.

The results do not include an estimated 480,000 special votes including postal and overseas ballots, so the full outcome will not be confirmed until next Friday. But with such strong support, the final outcome is not expected to change.

The "yes" verdict had been anticipated after multiple polls suggested strong public support for the law, which was also backed by Prime Minister Jacinda Ardern and the opposition leader, Judith Collins.

The vote will see New Zealand join a small group of countries, including the Netherlands and Canada, that allow euthanasia.

The referendum on assisted dying was held alongside the general election earlier this month as well as a separate non-binding referendum on legalising recreational cannabis. The preliminary results on the cannabis vote was 53.1% no and 46.1% yes.