The US Supreme Court has ruled that legally married same-sex couples should get the same benefits as heterosexual couples, in a major victory for the gay rights movement.

The court on Wednesday invalidated a provision of the federal Defence of Marriage Act (DOMA) that has prevented married gay couples from receiving a range of tax, health and retirement benefits that are generally available to married people.

The vote was 5-4.

Same-sex marriage has been adopted by 12 states and the District of Columbia. Another 18,000 couples were married in California during a brief period when same-sex unions were legal there.

Gay marriage in California

The Supreme Court also cleared the way for new same-sex marriages in California by holding that defenders of California's gay marriage ban did not have the right to appeal lower court rulings striking down the ban.

The court's vote on Wednesday leaves in place the initial trial court declaration that the ban is unconstitutional.

Al Jazeera's Kimberly Halkett, reporting from Washington DC, said gay rights called it a landmark day and a real turning point in terms of recognition under US law.

"The court ruled that Defence of Marriage Act (DOMA), passed in 1996, is unconstitutional and 'denies a single group of people protection under the fifth amendment of US constitution," our correspondent said.

"The court also ruled that Proposition 8 which passed in November 2008 California state elections does not have jurisdiction and that means - with less clarity - same sex marriage would be allowed to continue in California."

California officials probably will rely on the ruling to allow the resumption of same-sex unions in about a month's time.

The high court itself said nothing about the validity of gay marriage bans in California and roughly three dozen other states.

Same-sex couples burdened

"Under DOMA, same-sex married couples have their lives burdened, by reason of government decree, in visible and public ways," Kennedy said.

"DOMA's principal effect is to identify a subset of state-sanctioned marriages and make them unequal," he said. He was joined by the court's four liberal judges.

Chief Judge John Roberts and Judges Samuel Alito, Antonin Scalia and Clarence Thomas dissented.

Scalia read his dissent aloud. He said the court should not have decided the case.

But, given that it did, he said, "we have no power under the Constitution to invalidate this democratically adopted legislation".

The law was passed in 1996 by broad majorities in the House of Representatives and the Senate, and signed into law by Democratic President Bill Clinton.

Since then, many politicians who voted for the law and Clinton have renounced their support.