New York on Sunday was witness to hundreds of gay marriages.

New York State is the sixth in the nation, and so far the most populous, to sanction same-sex weddings. Beginning in the western town of Niagara Falls, gay and lesbian couples began exchanging marriage vows at the stroke of midnight, local time.

The greatest number of these marriages are taking place in New York City, where more than 800 couples registered in advance to get marriages licenses.

The New York legislature legalized same-sex marriage on June 24 but the law did not take effect until Sunday.

New York joined the midwestern state of Iowa and the New England states of Connecticut, Massachusetts, New Hampshire and Vermont and Washington, D.C. in legalizing gay marriage.

Federal law does not sanction such unions. But U.S. President Barack Obama has urged Congress to repeal the Defense of Marriage Act in the wake of New York's landmark decision, seen as a pivotal moment in the gay rights movement in the United States.