Emilio Alvarez-Icaza, president of the city's Human Right's Commission, said the law not only covers the city's gay, lesbian, transvestite, transsexual and transgender population, but also legalizes all forms of cohabitation.

The law means that couples can inherit property, pension and be the next of kin when one of the couple becomes ill.

Local authorities in the eastern Mexico City region of Iztapalapa were the first to start the same-sex weddings, with Antonio Medina and Jorge Cerpa celebrating a civil wedding at a public event.

The couple's witnesses included playwright Sabina Berman and the mayor of Iztapalapa Horacio Martinez.

The different delegations, as the city's sub-divisions are called, will have special offices for couples who decide to use the Cohabitation law.

Alejandro Diaz Garcia and Rafael Ramirez Arana, two advisors working for a deputy in Mexico's national legislature, formalized their union in the Venustiano Carranza delegation office.

"We know that this is not a wedding, and we don't want to make a spectacle of ourselves, nor to have anyone tell us we are crazy," said Ramirez.

The couple held a joint stag night with friends, and hosted a banquet at a hotel in the city's swank Paseo de La Reforma, before flying to Cancun, a tourist resort in the southeastern Mexico state of Quintana Roo for a honeymoon.