Mexican activists Javier Sicilia and Sergio Aguayo on Monday delivered to the U.S. Embassy in this capital a letter signed by more than 50,000 people in which they ask Washington for concrete measures to halt the "illegal and immoral" flow of weapons to Mexico.

In the letter, addressed to President Barack Obama, they expressed their condolences for "the frequent murders of innocents in your country" and said they are "deeply" moved by the recent massacre of children at an elementary school in Newtown, Connecticut.

However, they also expressed their bewilderment and indignation at "the indifference of the U.S. government toward the massacres that plunge Mexico into mourning," where more than 70,000 people died in conflicts involving rival criminal outfits and the security forces during the six-year term of President Felipe Calderon, which ended on Nov. 30.

Just in December, the first month of President Enrique Peña Nieto's term, "755 people were executed," most of them with firearms obtained in the United States, from where 70 percent of the arms seized in Mexico in the last three years come, according to U.S. government figures.

The concrete measures the activists and their supporters are asking Washington undertake include banning the importation of assault rifles manufactured abroad, among them the AK-47, the weapon of choice for Mexican gangsters.

At a press conference, Obama on Monday said that he will study possible executive action to try and put a damper on violence using firearms, basing it on the recommendations presented to him by Vice President Joe Biden in response to the Dec. 14 massacre in Newtown. EFE