Gay marriage proponents march down Sunset Boulevard in West Hollywood, California, 05 Nov 2008

Supporters of same-sex marriage have filed at least three lawsuits challenging a ban on gay marriage in California, after the state Tuesday approved an initiative to restrict marriage to heterosexual couples.

California residents voted to amend the constitution in Tuesday's general election by a vote of 52 to 48 percent in near complete results. Voters in Arizona and Florida also approved amendments to ban gay marriage in their respective states.

The results of the vote sparked angry demonstrations in California late Wednesday, as thousands of people marched in cities across the state, including Los Angeles and San Francisco, to protest the ban. Gay rights supporters chanted slogans and waved signs calling for the ban to be overturned.

It is unclear what will happen to the estimated thousands of homosexual couples who married after the state legalized same-sex marriage earlier this year.

In a 4-3 decision in May, the California Supreme Court ruled against a voter-approved law that restricted marriage to a man and a woman. The court said the state constitution's guarantee of equal rights gives same-sex couples the right to marry.

Tuesday's vote overturns that decision.

A number of U.S. states voted on other controversial issues in Tuesday's election.

Voters in Colorado and South Dakota rejected measures that would have criminalized abortion. The measure in Colorado would have defined life as beginning at the moment of conception, while the South Dakota initiative would have prohibited abortion except in cases of rape, incest and serious health threats to the mother.

Meanwhile, a ban on affirmative action policies based on race or gender passed in Nebraska, while voters in Washington approved a measure allowing terminally-ill patients to commit suicide with the help of a doctor.

Some information for this report was provided by AFP and AP.