The director of Mexico's chapter of the press freedom group Article 19 says the organization received a threatening letter and that he has filed a complaint with authorities.

Dario Ramirez says the typewritten letter that threatened him and the group's employees was slid under the door of their Mexico City offices before they arrived Friday morning.

The message threatens Ramirez with "beating him until his heart stops."

Ramirez says the organization has received threats over the phone before but nothing so "virulent" like the letter.

He says he is taking the threat seriously in light of the recent attacks against journalists and human rights activists.

Press advocates have long called Mexico one of the most dangerous nations for reporters.