Nearly two-thirds of voters backed legalizing same-sex marriage and giving gay couples the right to adopt in a referendum in Switzerland on Sunday.

The move will also allow married lesbian couples to have children through sperm donation, something that is currently only legal for married heterosexual couples, and it will make it easier for foreign spouses of a Swiss national to get citizenship.

Justice Minister Karin Keller-Sutter said after the vote that same-sex marriages could start taking place from July 1, 2022.

"Whoever loves each other and wants to get married will be able to do so, regardless of whether it is two men, two women, or a man and a woman," she said.

"The state does not have to tell citizens how they should lead their lives."

Same-sex couples in Switzerland are already able to register a civil partnership, but it does not provide the same rights as marriage, including for obtaining citizenship and the joint adoption of children.

Last December, the Swiss parliament finally approved a bill allowing same-sex couples to marry.

Opponents, however, gathered the 50,000 signatures required to put the issue to a referendum under the country's direct democracy system.

On Sunday, some 64.1 percent of voters chose to back more rights for the LGBT community, with the turnout at 52 percent. Notably, a majority in all 26 cantons voted yes, even the most conservative.

This makes Switzerland one of the last countries in western Europe to legalize gay marriage.

The right-wing populist Swiss People's Party (SVP) – Switzerland's largest political party – had called for a "no" vote, and in the run-up to the referendum, cities had been plastered with posters warning about "babies on order" and accusing proponents of putting their selfishness ahead of the well-being of children forced to grow up without a father.

For the gay community, however, Sunday was a major win. 

"It is a historic day for Switzerland, a historic day when it comes to equality for same-sex couples, and it is also an important day for the whole LGBT community," said Jan Muller of the "yes" campaign committee.

(With input from agencies)