MEXICO CITY - A new measure legalizing abortions in Mexico City was published into law yesterday, allowing doctors to almost immediately begin terminating pregnancies in the first trimester.

City Health Secretary Manuel Mondragon said that early-term abortions would be legal starting today and that doctors would be able to carry them out for women who were already at the 12-week legal limit and could not wait.

Women with less-advanced pregnancies will have to wait until regulations associated with the law have been published, probably next week. Girls under 18 would still need parental consent.

Mondragon also said that except in a medical emergency, women would have to prove residency in the capital, a city of nine million - correcting widespread belief that the law would make the capital a magnet for women across Mexico seeking abortions.

The law also allows gynecologists with moral objections to refuse to perform abortions.

The procedure will be free and available at 14 of the 28 city hospitals. Mondragon said each facility would be able to carry out seven abortions a day. Officials said it was not immediately clear whether private hospitals would have to offer the abortions.

The country's leading antiabortion group has said it may block entry to clinics performing abortions and to publicly identify abortion doctors.

President Felipe Calderon's conservative National Action Party also plans to challenge the new law before the Supreme Court, which could suspend its practice until a ruling were issued.

The law, backed by Mexico City's leftist government, is historic in a region with a heavy Roman Catholic majority.

Under the Mexico City law, women receiving an abortion after 12 weeks would face punishment of three to six months in jail, and anyone performing an abortion after the first trimester would face one to three years in jail.