MEXICO CITY ? Mexico City on Monday became Latin America's first municipality to approve gay marriage, an aide to a city lawmaker told AFP.

"It was approved overall by 39 votes in favor and 20 against, with five abstentions," said a spokesman for the bill's chief sponsor, assemblyman Davi Razu.

Spokesman Oscar Oliver said city legislators were now taking up a measure in the bill that would allow married same-sex couples to adopt children.

The new measure modified a civil union law already on the books in Mexico City, as in other Latin American nations including Uruguay and Colombia.

In Argentina the Supreme Court is to rule on a court-approved gay marriage that was challenged earlier this month.

Mexico City's gay marriage bill was fully backed in the Assembly by the city's majority leftist party, the Democratic Revolution Party, and opposed by the country's ruling National Action Party.

Before Monday's vote, Mexico City was among a handful of Latin American cities that allowed gay unions.